Radio wave sensor

Abstract

A radio wave sensor is provided with: an antenna unit including a plurality of antenna elements that transmit and receive radio waves; a housing which accommodates the antenna part; and a reflecting plate having a reflecting surface for reflecting a portion of the radio waves transmitted or received by the antenna unit, the antenna unit having an antenna region in which the plurality of antenna elements are disposed and which transmits and receives the radio waves, the reflecting plate being disposed such that the reflecting surface faces downward. When the antenna region is viewed from the front side, the front end of the reflecting surface is positioned above the center of the antenna region.

Description

TECHNICAL FIELD

[0001] The present disclosure relates to an electric wave sensor. This application claims priority based on Japanese Patent Application No. 2023-061237 filed on April 5, 2023, and incorporates by reference the entire disclosure of the Japanese Patent Application. BACKGROUND

[0002] In an electric wave sensor for traffic monitoring, an object (vehicle, pedestrian, or the like) set in a detection zone on a road is detected. The electric wave sensor is disposed obliquely downward with a wave irradiation surface in a manner of irradiating an electric wave to a detection zone in front at a high position such as the vicinity of the upper end of a support, but a position in the vicinity of the directly below of the electric wave sensor easily becomes a blind zone. Due to the limitation of the disposition position of the electric wave sensor, it is sometimes necessary to include the vicinity of the directly below of the electric wave sensor in the detection zone.

[0003] Patent Literature 1 discloses an electric wave sensor including a transmission section capable of limiting an irradiation range to a first zone and transmitting an electric wave from a first antenna, wherein the first zone is a zone of a start portion of a pedestrian crossing and is a zone not including the entire above-mentioned pedestrian crossing; a reception section that receives an electric wave from the above-mentioned first zone; and a detection section that detects an object in the above-mentioned first zone based on the electric wave received by the above-mentioned reception section. The transmission section of the electric wave sensor disclosed in Patent Literature 1 is also capable of limiting the irradiation range to a second zone including a portion of the pedestrian crossing farther from the electric wave sensor than the first zone and transmitting an electric wave from a second antenna, the reception section also receives an electric wave from the second zone, and the detection section also detects an object in the second zone based on the electric wave from the second zone received by the reception section.

[0004] PRIOR ART DOCUMENTS

[0005] PATENT LITERATURE

[0006] Patent Literature 1: Japanese Patent Application Publication No. 2015-148578 SUMMARY

[0007] An electric wave sensor of one aspect of the present disclosure includes an antenna section including a plurality of antenna elements that transmit and receive an electric wave; a housing that houses the antenna section; and a reflection plate having a reflection surface that reflects a portion of the electric wave transmitted or received by the antenna section, the antenna section having an antenna region as a region in which the plurality of antenna elements are disposed and transmit and receive the electric wave, the reflection plate being disposed in a manner that the reflection surface faces downward, a front end of the reflection surface being located higher than a center of the antenna region when the antenna region is viewed from the front.

[0008] The present disclosure includes, in addition to the above-described electric wave sensor, an antenna reflector including the configuration included in the electric wave sensor. BRIEF DESCRIPTION OF DRAWINGS

[0009] Figure 1 FIG. 1 is a diagram showing an example of use of the electric wave sensor of the embodiment.

[0010] Figure 2 FIG. 2 is a perspective view showing one example of the configuration of the electric wave sensor of the embodiment.

[0011] Figure 3 FIG. 3 is a perspective view showing one example of the internal configuration of the electric wave sensor of the embodiment.

[0012] Figure 4A FIG. 4 is a diagram for explaining one example of the electric wave irradiation range of the electric wave sensor in which no reflector is provided.

[0013] Figure 4B FIG. 5 is a diagram for explaining one example of the electric wave irradiation range of the electric wave sensor of the embodiment.

[0014] Figure 5A FIG. 6 is a side view of a circuit board and a reflector showing one example of the positional relationship between the antenna region and the reflector surface.

[0015] Figure 5B FIG. 7 is a side view of a circuit board and a reflector showing another example of the positional relationship between the antenna region and the reflector surface.

[0016] Figure 5C FIG. 8 is a side view of a circuit board and a reflector showing still another example of the positional relationship between the antenna region and the reflector surface.

[0017] Figure 6 FIG. 9 is a perspective view of a circuit board and a reflector showing one example of the positional relationship between the antenna region and the reflector surface in the first direction X.

[0018] Figure 7A FIG. 10 is a perspective view showing the configuration of the antenna with a reflector used for simulation.

[0019] Figure 7B FIG. 11 is a front view showing the configuration of the antenna with a reflector used for simulation.

[0020] Figure 7C FIG. 12 is a side view showing the configuration of the antenna with a reflector used for simulation.

[0021] Figure 8A FIG. 13 is a graph showing the simulation result of the horizontal plane directivity of the antenna without a reflector.

[0022] Figure 8Bis a graph showing simulation results of the vertical plane directivity of the antenna without the reflector.

[0023] Figure 9A is a graph showing simulation results of the horizontal plane directivity of the antenna with the reflector.

[0024] Figure 9B is a graph showing simulation results of the vertical plane directivity of the antenna with the reflector.

[0025] Figure 10 is a graph showing the walking pattern of the subject in the performance evaluation experiment.

[0026] Figure 11A is a graph showing results of the performance evaluation experiment of the antenna without the reflector.

[0027] Figure 11B is a graph showing results of the performance evaluation experiment of the antenna with the reflector manufactured in a manner shown in Figure 9A and Figure 9B .

[0028] Figure 12 is a side view of a circuit board and a reflector for explaining the setting of the positions of the front end and the base end of the reflector surface.

[0029] Figure 13A is a graph showing simulation results of the horizontal plane directivity in the case of θ1= 80°, θ2= 25°.

[0030] Figure 13B is a graph showing simulation results of the vertical plane directivity in the case of θ1= 80°, θ2= 25°.

[0031] Figure 14A is a graph showing simulation results of the horizontal plane directivity in the case of θ1= 75°, θ2= 25°.

[0032] Figure 14B is a graph showing simulation results of the vertical plane directivity in the case of θ1= 75°, θ2= 25°.

[0033] Figure 15A is a graph showing simulation results of the horizontal plane directivity in the case of θ1= 70°, θ2= 25°.

[0034] Figure 15B is a graph showing simulation results of the vertical plane directivity in the case of θ1= 70°, θ2= 25°.

[0035] Figure 16A is a graph showing simulation results of the horizontal plane directivity in the case of θ1= 80°, θ2= 30°.

[0036] Figure 16B is a graph showing the simulation results of the vertical plane directivity in the case of θ1= 80°, θ2= 30°.

[0037] Figure 17A is a graph showing the simulation results of the horizontal plane directivity in the case of θ1= 80°, θ2= 35°.

[0038] Figure 17B is a graph showing the simulation results of the vertical plane directivity in the case of θ1= 80°, θ2= 35°.

[0039] Figure 18 is a graph for explaining the reflection regions in the reflecting surface.

[0040] Figure 19 is a front view showing the configuration of one antenna element.

[0041] Figure 20 is a graph showing one example of the setting of the length of the reflecting surface in the first direction.

[0042] Figure 21A is a graph showing the simulation results of the horizontal plane directivity in the case of a = 10.

[0043] Figure 21B is a graph showing the simulation results of the vertical plane directivity in the case of a = 10.

[0044] Figure 22A is a graph showing the simulation results of the horizontal plane directivity in the case of a = 4.

[0045] Figure 22B is a graph showing the simulation results of the vertical plane directivity in the case of a = 4.

[0046] Figure 23A is a graph showing the simulation results of the horizontal plane directivity in the case of a = 1.

[0047] Figure 23B is a graph showing the simulation results of the vertical plane directivity in the case of a = 1.

[0048] Figure 24A is a graph showing the simulation results of the horizontal plane directivity in the case where X3 is changed at 1 mm intervals in the range of 1 to 20 mm.

[0049] Figure 24B is a graph showing the simulation results of the vertical plane directivity in the case where X3 is changed at 1 mm intervals in the range of 1 to 20 mm.

[0050] Figure 25 is a perspective view of a first modification example of the electric wave sensor of the embodiment.

[0051] Figure 26 is a perspective view of a second modification example of the electric wave sensor of the embodiment.

[0052] Figure 27 is a perspective view of a third modification example of the electric wave sensor of the embodiment.

[0053] Figure 28 is a perspective view of a fourth modification example of the electric wave sensor of the embodiment. DETAILED DESCRIPTION

[0054] [Problem to be Solved by the Disclosure]

[0055] In the device disclosed in Patent Literature 1, in order to expand the detection area, a second antenna needs to be provided separately from the first antenna.

[0056] [Effects of the Disclosure]

[0057] According to the disclosure, the detection area of the electric wave sensor can be expanded without increasing the number of antennas.

[0058] <Summary of Embodiments of the Disclosure>

[0059] Hereinafter, a summary of the embodiments of the disclosure will be described.

[0060] (1) The electric wave sensor of the embodiment includes an antenna section including a plurality of antenna elements that transmit and receive electric waves, a housing that accommodates the antenna section, and a reflection plate having a reflection surface that reflects a part of the electric waves transmitted or received by the antenna section, the antenna section having an antenna area as an area in which the plurality of antenna elements are arranged and transmit and receive the electric waves, the reflection plate being arranged with the reflection surface facing downward, the front end of the reflection surface being located higher than the center of the antenna area when the antenna area is viewed from the front. Thus, the electric wave radiated from the antenna section toward the front can be suppressed from being blocked, and the electric wave toward the upper side can be reflected toward the lower side. Therefore, the detection area of the electric wave sensor can be expanded without increasing the number of antennas.

[0061] (2) In the above (1), the front end of the reflection plate can be located higher than the upper end of the antenna area. Thus, the main lobe of the electric wave radiated from the antenna section can be further suppressed from being blocked.

[0062] (3) In the above (1) or (2), the antenna section can further have an antenna surface that is a plane in which the plurality of antenna elements are arranged in a first direction that is a horizontal direction, and an angle formed by a first straight line connecting a front end of the reflecting surface and a center of the antenna region and the antenna surface in a plane perpendicular to the first direction is equal to or greater than 75°. Thus, the front end of the reflecting plate is located in a range in which the intensity of the electric wave is high, and the gain of the lower portion of the antenna section can be increased.

[0063] (4) In the above (3), an angle formed by a second straight line connecting a base end of the reflecting plate and the center of the antenna region and the antenna surface in the plane perpendicular to the first direction can be equal to or less than 30°. Thus, the base end of the reflecting plate is located in a range in which the intensity of the electric wave is high, and the gain of the lower portion of the antenna section can be increased. Here, the "base end" refers to an end opposite the front end. Specifically, the "base end" refers to an assembly end of the reflecting plate to a member (for example, a housing) that supports the reflecting plate.

[0064] (5) In any one of the above (1) to (4), an angle formed by the reflecting surface and the antenna surface can be in a range of 60° to 90°. Thus, the electric wave can be reflected to a position close to the electric wave sensor, and the detection area can be expanded.

[0065] (6) In any one of the above (1) to (5), a length of the reflecting surface along the first direction can be equal to or greater than a length of the antenna region along the first direction. Thus, a majority of the side lobe toward the upper portion can be reflected.

[0066] (7) In the above (6), the length of the reflecting surface along the first direction can be a length including a plurality of reflecting regions determined for each of the plurality of antenna elements. Thus, the electric wave radiated from each antenna element can be reflected by the reflecting plate, and the gain of the antenna can be increased.

[0067] (8) In the above (7), a length of the reflecting region along the first direction can be equal to or greater than 4 times a length of the antenna element in the first direction. Thus, the reflecting plate is located in a range in which the intensity of the electric wave is high in the first direction, and the gain of the lower portion of the antenna section can be increased.

[0068] (9) In the above (7) or (8), the reflecting region can include a region in which the intensity of the electric wave radiated from the antenna element is equal to or greater than -3 dB with respect to the peak value of the main lobe. Thus, the electric wave of sufficient intensity (equal to or greater than -3 dB) can be reflected without omission, and the gain of the lower portion of the antenna section can be increased.

[0069] (10) In any one of (1) to (9) above, the radio wave sensor can further include a holding portion that holds the antenna portion, and the reflection plate can be attached to the holding portion. Thus, the reflection plate can be disposed in the vicinity of the antenna portion, and the attachment position of the reflection plate with respect to the antenna portion can be regulated.

[0070] (11) In any one of (1) to (10) above, the housing can house the reflection plate. Thus, the reflection plate can be protected from rain and the like, and the position of the reflection plate can be regulated.

[0071] (12) In any one of (1) to (11) above, the reflection plate can be a rectangular flat plate. Thus, the reflection plate can be configured simply.

[0072] (13) In any one of (1) to (11) above, the reflection plate can be a plate-shaped having a bent portion in a portion away from the antenna portion, the reflection plate can include a first portion closer to the antenna portion than the bent portion and a second portion farther from the antenna portion than the bent portion, and the second portion can form an angle smaller than an angle formed by the first portion and the antenna face. Thus, the detection area can be extended to a position close to the radio wave sensor.

[0073] (14) In any one of (1) to (4) and (6) to (11) above, the reflection plate can be a plate-shaped curved in a manner that the front end is lowered. Thus, the detection area can be extended to a position close to the radio wave sensor.

[0074] (15) In any one of (1) to (14) above, the front end of the reflection plate can have a shape based on an intensity distribution of radio waves reflected by the reflection face. Thus, a high radio wave intensity can be ensured, and a small reflection plate can be configured.

[0075] (16) In any one of (1) to (15) above, the reflection face can radiate a reflected wave obtained by reflecting the radio wave toward a second radiation range, the second radiation range being a radiation range closer to the radio wave sensor than a first radiation range in which the radio wave is radiated from the antenna portion to the ground without being reflected by the reflection face. Thus, the detection area can be extended to a position close to the radio wave sensor.

[0076] (17) The electric wave sensor of the embodiment includes an antenna section including a plurality of antenna elements that transmit and receive electric waves, a housing that houses the antenna section, and a reflection plate that reflects a portion of the electric waves transmitted or received by the antenna section, the reflection plate being disposed with a reflection surface that reflects the electric waves facing downward, a front end of the reflection plate being located above a central axis of a main lobe irradiated from the antenna section. Thus, the main lobe irradiated from the antenna section can be prevented from being blocked, and a side lobe directed upward can be reflected downward. Therefore, the detection area of the electric wave sensor can be expanded without increasing the antenna.

[0077] <Details of the Embodiments of the Present Disclosure>

[0078] Details of the embodiments of the present disclosure will be described below with reference to the drawings. Note that at least a part of the embodiments described below can be arbitrarily combined.

[0079] [1. Configuration of Electric Wave Sensor]

[0080] Reference Signs Figure 1 The electric wave sensor 100 of the embodiment is a wave radar for traffic monitoring, and detects pedestrians in a pedestrian crossing 20.

[0081] The electric wave sensor 100 is attached to a structure 50 provided on a sidewalk 61B. The structure 50 has a height of several m, and the electric wave sensor 100 is disposed at a height of several m above the ground.

[0082] The electric wave sensor 100 detects objects (e.g., pedestrians, bicycles, and vehicles) on the pedestrian crossing 20 by irradiating electric waves (millimeter waves) on the pedestrian crossing 20 and receiving reflected waves thereof. More specifically, the electric wave sensor 100 detects the distance from the electric wave sensor 100 to the objects on the pedestrian crossing 20, the speed of the objects, and the horizontal angle (hereinafter referred to as "azimuth angle") of the position of the objects with respect to the electric wave irradiation axis (central axis of the main lobe).

[0083] As described later, the electric wave sensor 100 is provided with a reflection plate 130, and detects objects using millimeter waves reflected by the reflection plate 130. When reflected by the reflection plate 130, the path length of the electric waves becomes longer. However, when an object such as a pedestrian, a bicycle, or a vehicle, which is sufficiently larger than the wavelength (1 mm to 10 mm) of the millimeter waves, is detected, the increase in the path length of the electric waves caused by the reflection plate 130 is within the error range, and the detection accuracy is not substantially reduced.

[0084] People crossing at pedestrian crossing 20 and those waiting to cross for a signal are referred to as "passengers". Passengers include pedestrians and bicycles (more specifically, bicycles ridden by riders). Radio wave sensor 100 detects passengers and their position (distance and azimuth) and speed.

[0085] Reference Figure 2 The radio wave sensor 100 includes a circuit board 110, a reflector 130, and a housing 150.

[0086] The circuit board 110 and the reflector 130 are housed in the housing 150. The housing 150 is an example of a "receiving part".

[0087] The circuit board 110 includes an antenna section 120. The outer casing 150 is, for example, a cuboid, with one side being the radio wave transmitting and receiving surface.

[0088] Reference Figure 3 . Figure 3 The circuit board 110 and the reflector 130 are shown.

[0089] The circuit board 110 is flat. Hereinafter, a direction along the main surface of the circuit board 110 will be referred to as the first direction X. A direction along the main surface of the circuit board 110 that is orthogonal to the first direction X will be referred to as the second direction Y. A direction orthogonal to the first direction X and the second direction Y will be referred to as the third direction Z. The third direction Z is the normal direction of the main surface of the circuit board 110 and is the direction from the main surface of the circuit board 110 toward the radio wave transceiver surface of the housing 150.

[0090] The electromagnetic wave sensor 100 is positioned such that the second direction Y is upward. If the first end of the circuit board 110 in the second direction Y (in...) Figure 3 The middle end (near the reflector 130) is located on the upper side, and the second end (in the second direction Y of the circuit board 110) is located on the upper side. Figure 3 If the end furthest from the reflector 130 is located on the lower side, then the front of the housing 150 of the radio wave sensor 100 can be tilted downwards. Hereinafter, for simplicity, the second direction Y will be referred to as "above," and the opposite direction of the second direction Y will be referred to as "below." The first direction X will also be referred to as "left," and the opposite direction of the first direction X will be referred to as "right." The third direction Z will also be referred to as "front," and the opposite direction of the third direction Z will be referred to as "rear."

[0091] In addition to the antenna section 120, the circuit board 110 also includes a detection and processing circuit 111, a power supply circuit 112, and an interface section 113. The circuit board 110 is, for example, a printed circuit board, and the antenna section 120, the detection and processing circuit 111, the power supply circuit 112, and the interface section 113 are each configured as part of the circuit of the circuit board 110.

[0092] The antenna section 120 includes receiving antenna elements 121a, 121b, 121c, and 121d, and transmitting antenna elements 121e, 121f, and 121g. The transmitting antenna elements 121e, 121f, and 121g illuminate (transmit) radio waves, and the receiving antenna elements 121a, 121b, 121c, and 121d receive radio waves.

[0093] The antenna section 120 is, for example, an array antenna. Specifically, the receiving antenna elements 121a, 121b, 121c, and 121d constitute a receiving array antenna, and the transmitting antenna elements 121e, 121f, and 121g constitute a transmitting array antenna. Hereinafter, the "receiving antenna element" and the "transmitting antenna element" will also be referred to as "antenna elements".

[0094] like Figure 3 As shown, antenna elements 121a, 121b, 121c, 121d, 121e, 121f, and 121g are arranged in a horizontal column. Receiving antenna elements 121a, 121b, 121c, and 121d are arranged in a left-right column, and transmitting antenna elements 121e, 121f, and 121g are also arranged in a left-right column.

[0095] Antenna section 120 includes antenna region 125, which includes receiving antenna elements 121a, 121b, 121c, 121d and transmitting antenna elements 121e, 121f, 121g. Antenna region 125 is the area for transmitting and receiving radio waves from antenna section 120. Receiving antenna elements 121a, 121b, 121c, 121d and transmitting antenna elements 121e, 121f, 121g are formed on the surface of circuit board 110. Therefore, antenna region 125 is a region in the XY plane.

[0096] The left end of antenna region 125 coincides with the left end of the leftmost antenna element 121a among antenna elements 121a, 121b, 121c, 121d, 121e, 121f, and 121g. The right end of antenna region 125 coincides with the right end of the rightmost antenna element 121g among antenna elements 121a, 121b, 121c, 121d, 121e, 121f, and 121g. The upper end of antenna region 125 coincides with the upper end of the uppermost antenna element 121f among antenna elements 121a, 121b, 121c, 121d, 121e, 121f, and 121g. The lower end of antenna region 125 coincides with the lower end of antenna elements 121a, 121b, 121c, 121d, 121e, and 121g. That is to say, antenna region 125 is a rectangular region with the smallest area surrounding antenna elements 121a, 121b, 121c, 121d, 121e, 121f, and 121g.

[0097] The detection processing circuit 111 generates a modulated wave. The generated modulated wave is transmitted from the transmission antenna elements 121e, 121f, 121g. The transmitted modulated wave hits an object (e.g., a pedestrian, a bicycle, a vehicle) and is reflected.

[0098] In order to detect the azimuth angle of the object, a plurality of (four in the figure) reception antenna elements 121a, 121b, 121c, 121d are used. The detection processing circuit 111 performs signal processing on the received reflected wave. The detection processing circuit 111 analyzes the reflected wave data generated by the signal processing to detect the position (distance and azimuth angle) and speed of the object.

[0099] The interface section 113 is a circuit for communicating with an external device. The interface section 113 includes a connector not shown, and can be connected to an external device via a cable. The interface section 113 can transmit data of the detection result to the connected external device. Alternatively, the interface section 113 can be a wireless communication interface, and can communicate with an external device by wireless.

[0100] The power supply circuit 112 supplies power to the detection processing circuit 111.

[0101] A reflection plate 130 is disposed above the circuit board 110. The reflection plate 130 is, for example, a rectangular flat plate. In a specific example, the circuit board 110 and the reflection plate 130 are fitted to the inner surface of the housing 150. The inner surface of the housing 150 is a holding portion that holds the circuit board 110, and the reflection plate 130 is fitted to the holding portion. The fitting structure of the circuit board 110 and the reflection plate 130 is not limited to this. For example, the circuit board 110 and the reflection plate 130 can be fitted to a holding member fixed to the inner surface of the housing 150.

[0102] The reflection plate 130 includes a reflection surface 131 (see FIG. 1) for reflecting an electric wave. The reflection surface 131 is disposed at a position that reflects a part of the electric wave transmitted from the antenna section 120. The reflection surface 131 reflects the electric wave toward the obliquely downward direction, toward the road obliquely downward of the electric wave sensor 100, and in the example, mainly toward the lane 60 and the sidewalk 61A. Figure 4B ) toward the obliquely downward direction, toward the road obliquely downward of the electric wave sensor 100, and in the example, mainly toward the lane 60 and the sidewalk 61A. Figure 1

[0103] The reflection surface 131 is provided to the lower surface of the reflection plate 130. For example, the reflection plate 130 is composed of a metal. In this case, the lower surface of the reflection plate 130 is the reflection surface 131. In another example, the reflection plate 130 can also be composed of a holding plate made of synthetic resin, and a metal plate is fitted to the lower surface of the holding plate. In this case, the lower surface of the metal plate is the reflection surface 131.

[0104] [2. Expansion of the detection area by the reflection plate]​

[0105] Referring to Figure 1 A detection area 30A, 30B is set as a range on a road for detecting an object. The detection area 30A, 30B is set as a part of the radio wave irradiation area 40A, 40B of the radio wave sensor 100.

[0106] The radio wave irradiation area 40A is a range in which radio waves are directly irradiated from the antenna section 120 of the radio wave sensor 100. The radio wave irradiation area 40B is a range in which radio waves that have been reflected by the reflection plate 130 among radio waves transmitted from the antenna section 120 of the radio wave sensor 100 are irradiated.

[0107] For example, the detection area 30A is set inside the radio wave irradiation area 40A. The detection area 30B is set inside the radio wave irradiation area 40B.

[0108] Pedestrian waiting areas 21A, 21B are provided at both ends of the pedestrian crosswalk 20 connected to the sidewalks 61A, 61B. The waiting areas 21A, 21B are set on the sidewalks 61A, 61B provided on both sides of the lane 60. Pedestrians wait in the waiting areas 21A, 21B for the pedestrian signal 10 to switch from a red light (prohibition of passage) to a green light (permission of passage).

[0109] The structure 50 equipped with the radio wave sensor 100 is provided, for example, to the sidewalk 61B that is one of the sidewalks 61A, 61B on both sides of the lane 60. Hereinafter, the waiting area 21A provided to the sidewalk 61A on which the radio wave sensor 100 is not provided will be referred to as a "first waiting area 21A", and the waiting area 21B provided to the sidewalk 61B on which the radio wave sensor 100 is provided will be referred to as a "second waiting area 21B".

[0110] The detection area 30A is an area including the pedestrian crosswalk 20 and the first waiting area 21A. The detection area 30B is an area including the second waiting area 21B. The radio wave irradiation area 40B is set at a position closer to the radio wave sensor 100 than the radio wave irradiation area 40A.

[0111] Referring to Figure 1 and Figure 4A Radio waves are radiated from the radio wave sensor 100A in a radial manner. The setting angle of the radio wave sensor 100A is adjusted in such a manner that the first waiting area 21A of the sidewalk 61A can be sensed without omission and the radio wave irradiation axis is directed as much as possible downward. The radio wave irradiation axis is an axis that passes through the center of the transceiving surface and is perpendicular to the transceiving surface. The radio wave irradiation axis is adjusted in such a manner that the radio wave irradiation axis is directed as much as possible downward in the plane perpendicular to the transceiving surface. Figure 4AThe gain is highest in the directivity of the YZ plane. Radio wave sensor 100A is installed on sidewalk 61B. Radio wave sensor 100A is not installed on sidewalk 61A on the opposite side of sidewalk 61B, across lane 60. A portion of the radio wave is irradiated obliquely upwards from the radio wave sensor 100A thus installed.

[0112] The height of pedestrians (or vehicles) at pedestrian crossing 20 is the detection target, and the distance between the pedestrian (or vehicle) and the ground is less than or equal to h. Therefore, the radio wave sensor 100A only needs to detect objects at a height less than or equal to h. That is to say, radio waves irradiated above a height greater than h are not used for object detection.

[0113] In the direction close to the radio wave sensor 100A (structure 50), a second waiting area 21B is provided at a distance of, for example, greater than or equal to 2m from the boundary between the pedestrian crossing 20 and the sidewalk 61B (see reference). Figure 1 Here, the distance from the end of the second waiting area 21B of the pedestrian walkway 61B, which is equipped with the radio wave sensor 100, near the structure 50, to the location of the structure 50 is referred to as the "set back distance". The set back distance must be greater than the width of the second waiting area 21B. In order to set a second waiting area 21B with a width of 2m or greater, the set back distance needs to be greater than or equal to 2m.

[0114] In the radio wave sensor 100A without reflector 130, a sufficiently high intensity radio wave cannot be irradiated into the second waiting area 21B unless the backlash distance is sufficiently increased. The detection accuracy of objects in the second waiting area 21B may decrease. Depending on the layout of the sidewalk 61B where the radio wave sensor 100A is installed, it is sometimes difficult to ensure a large backlash distance. The freedom of placement for the radio wave sensor 100A is limited. In contrast, in the radio wave sensor 100 with reflector 130, a sufficiently high intensity radio wave can be irradiated into the second waiting area 21B even without increasing the backlash distance. Therefore, the freedom of placement for the radio wave sensor 100 is increased.

[0115] Reference Figure 4B Transmitting antenna elements 121e, 121f, and 121g transmit radio waves toward the detection area 30A. Receiving antenna elements 121a, 121b, 121c, and 121d receive reflected waves obtained by the radio waves being reflected by objects within the detection area 30A. Hereinafter, the reflected waves reflected by objects within the detection area 30A and received directly (without via reflector 130) by receiving antenna elements 121a, 121b, 121c, and 121d will also be referred to as "direct reflected waves".

[0116] A portion of the radio waves transmitted from transmitting antenna elements 121e, 121f, and 121g are directed toward reflector 130. The radio waves reflected by reflector 130 illuminate detection area 30B. Receiving antenna elements 121a, 121b, 121c, and 121d receive the reflected waves from objects within detection area 30B via reflector 130. Hereinafter, the reflected waves reflected by objects within detection area 30B and received by receiving antenna elements 121a, 121b, 121c, and 121d via reflector 130 will also be referred to as "indirect reflected waves."

[0117] In this embodiment, a portion of the radio waves emanating upwards from the radio wave sensor 100 is reflected by the reflector 130 and directed towards the ground. As described above, the upward-emanating radio waves are not used for object detection. However, object detection can be utilized by having the reflector 130 reflect the upward-emanating radio waves and direct them towards the ground.

[0118] The area 40B where the radio waves are reflected by the reflector 130 is closer to the radio wave sensor 100 than the area 40A. Therefore, even with a reduced backlash distance, radio waves can still be irradiated into the second waiting area 21B.

[0119] [3. Positional relationship between the antenna region and the reflector surface]

[0120] The positional relationship between the antenna region 125 and the reflector surface 131 will be explained below.

[0121] Reference Figure 5A .

[0122] As described above, antenna region 125 is a region that is part of the surface of antenna section 120, but... Figure 5A For ease of understanding, the antenna region 125 is shown with a thick solid line. In the radio wave sensor 100 of this embodiment, when the antenna region 125 is viewed from the front, the front end of the reflective surface 131 is located above the center of the antenna region 125. Assuming a central axis 140 extending from the center 140a of the antenna region 125 along the normal direction (third direction Z), the central axis 140 does not overlap with the reflective surface 131. The central axis 140 is located below the reflective surface 131.

[0123] exist Figure 5A In this example, more specifically, the front end of the reflector 131 is located above the upper end of the antenna region 125. The front end of the reflector 131 and the upper end of the antenna region 125 are separated by a distance Y1 in the vertical direction.

[0124] The central axis 140 is the radio wave illumination axis. The main lobe is illuminated from the antenna region 125 along the central axis 140. Therefore, most of the main lobe is not blocked by the reflector 131.

[0125] Here, the "front end of the reflecting surface 131 is located above the center of the antenna area 125" means that the portion of the reflecting surface 131 corresponding to the center axis 140 of the antenna area 125 is located above the center axis 140 in the X direction. For example, even if a portion of the front end of the reflecting plate 130 protrudes and the protruding front end is located below the center axis 140, it is included in the "front end of the reflecting surface 131 is located above the center of the antenna area 125" if at least the portion of the reflecting surface 131 corresponding to the center axis 140 of the antenna area 125 (for example, the central portion of the reflecting surface 131 in the X direction) is located above the center axis 140. In this case, the center axis 140 does not overlap the reflecting surface 131, and thus the main lobe is not blocked by the reflecting surface 131.

[0126] For example, the center axis 140 is the center axis of the main lobe. That is, the front end of the reflecting surface 131 is located above the center axis of the main lobe.

[0127] The center axis of the main lobe can also be different from the center axis 140 of the antenna area 125. For example, the main lobe can be radiated from the antenna area 125 in a downwardly inclined direction by beamforming. In this case, the center axis of the main lobe extends in a direction different from the normal direction of the antenna area 125.

[0128] Reference Signs List Figure 5B , Figure 5C .

[0129] The reflecting plate 130 can also be inclined in a manner in which the front end is lowered. However, as in the example of Figure 5A , the center axis 140 is required to be located below the front end of the reflecting surface 131.

[0130] In the example of Figure 5B , the front end of the reflecting surface 131 is located above the upper end of the antenna area 125. The front end of the reflecting surface 131 is separated from the upper end of the antenna area 125 in the vertical direction by a distance Y2. Thus, in the example of Figure 5B , the main lobe is also not blocked by the reflecting surface 131.

[0131] In the example of Figure 5C , the front end of the reflecting surface 131 is located above the center axis 140 of the antenna area 125 but below the upper end of the antenna area 125. Even with such a configuration, only a portion of the upper side of the main lobe is blocked by the reflecting surface 131, and a sufficient range of the main lobe is ensured.

[0132] However, it is not desirable that the front end of the reflecting surface 131 is located lower than the center of the antenna area 125. When the reflecting surface 131 is set to such a range, most of the main lobe is reflected by the reflecting surface 131, and the gain of the electric wave sensor is reduced.

[0133] Next, the positional relationship between the antenna area 125 and the reflecting surface 131 in the first direction X is described. Referring to Figure 6 .

[0134] In Figure 6 , Xl is the length of the reflecting surface 131 in the first direction X, and X2 is the length of the antenna area 125 in the first direction. As described above, the antenna elements 121a, 121b, 121c, 121d, 121e, 121f, and 121g are arranged in the first direction X (refer to Figure 3 ). Therefore, Xl is the length of the reflecting surface 131 in the first direction X as the arrangement direction of the antenna elements 121a, 121b, 121c, 121d, 121e, 121f, and 121g, and X2 is the length of the antenna area 125 in the first direction X.

[0135] As shown in Figure 6 , the length Xl of the reflecting surface 131 is longer than the length X2 of the antenna area 125. Thereby, most of the electric wave radiated upward from the antenna area 125 can be reflected by the reflecting surface 131.

[0136] [4. Setting of the configuration of the reflecting surface]

[0137] The inventors constructed a model of an antenna with a reflecting plate and a model of an antenna without a reflecting plate on a computer and performed simulation of antenna directivity.

[0138] Referring to Figure 7A , Figure 7B , Figure 7C .

[0139] The lateral width of the reflecting plate 130X was 70 mm, and the longitudinal length of the reflecting plate 130X was 25 mm. The entire lower surface of the reflecting plate 130X was a reflecting surface. The lateral width of the antenna portion 120X was 47 mm, and the height of the antenna portion 120X was 8 mm. The base end of the reflecting plate 130X was connected to the upper end of the antenna portion 120X, and the angle (YZ plane angle) formed by the reflecting plate 130X and the antenna portion 120X was 71°. When the antenna area of the antenna portion 120X was observed from the front, the size and the angle of the reflecting plate 130X were determined in such a manner that the front end of the reflecting plate 130X was located higher than the center of the antenna area. The angle formed by the reflecting plate 130X and the antenna portion 120X can be set in the range of 60° to 90°. Thereby, a reflected wave can be radiated to a region close to the antenna.

[0140] Referring to Figure 8A and Figure 8B Referring to Figure 9A and Figure 9B In Figure 8A and Figure 9A , the arrow length indicates the gain (dBi), and the angle indicates the angle around the center 140a on the XY plane (the direction of the center axis 140 is set to 0°). In Figure 8B and Figure 9B , the arrow length indicates the gain (dB), and the angle indicates the angle around the center 140a on the YZ plane (the direction of the center axis 140 is set to 0°). The same applies to the following graphs.

[0141] When Figure 8A is compared with Figure 9A , in the test machine, approximately the same horizontal plane directivity as the antenna without the reflecting plate is obtained.

[0142] When Figure 8B is compared with Figure 9B , in the test machine, the gain is improved at 50° to 60° (particularly, around 57°) lower than the antenna without the reflecting plate. In the test machine, the gain in the range of 50° to 90° upper than the antenna without the reflecting plate is reduced. Such increase and decrease of the gain is due to the reflecting plate 130X being provided.

[0143] The reduction of the gain in the range of 50° to 90° upper is considered to be due to the electric wave radiated to the range being reflected by the reflecting plate 130X. The increase of the gain in the range of 50° to 60° lower is considered to be due to the electric wave in the range of 50° to 90° upper being reflected by the reflecting plate 130X toward the range of 50° to 60° lower.

[0144] The inventors manufactured the antenna with the reflecting plate shown in Figure 9A and Figure 9B in the manner of the antenna directivity shown in Figure 7A , 7B , 7C, and conducted a performance evaluation experiment of evaluating the detection performance of the antenna without the reflecting plate and the test machine. Referring to Figure 10 In the performance evaluation experiment, the antenna without the reflecting plate and the test machine respectively detected the radio wave in Figure 10The experiment was conducted on subjects walking in the pattern shown. In walking mode, the subjects walked 7m forward (as the Z1 direction obtained by projecting the Z direction onto the ground) directly below the radio wave sensor 100, then walked 2m to the right (X direction), then walked 7m backward, and then walked 2m to the right again. The pedestrian started walking in the Z1 direction from a position (Z1, X) of (0, 0) relative to the radio wave sensor (in [m]), changed direction in the X direction at the time point of reaching position (7, 0), changed direction in the -Z1 direction at the time point of reaching position (7, 2), changed direction in the -X direction at the time point of reaching position (0, 2), and returned to position (0, 0). In the experiment, for each of the radio wave sensor 100R equipped with an antenna without a reflector and the radio wave sensor 100X equipped with an antenna with a reflector from a prototype, the position of the subject was detected by the radio wave sensor 100R and the radio wave sensor 100X, respectively, during the subject's walking in the above-described mode.

[0145] Reference Figure 11A , Figure 11B . Figure 11A and Figure 11B The detection results output by the aforementioned radio wave sensors 100R and 100X at specified periods are shown in superimposed form. Figure 11A and Figure 11B In the diagram, the vertical axis represents the distance to the radio wave sensors 100R and 100X in the Z1 direction, and the horizontal axis represents the distance to the radio wave sensors 100R and 100X in the X direction. For example... Figure 11A As shown in the dashed box, in an antenna without a reflector, the subject cannot be detected within a range of 3 meters in front of the radio wave sensor 100R. Figure 11B As shown in the dashed box, the prototype can detect the subject within a range of 3m in front of the radio wave sensor 100X. It can be seen that the prototype also exhibits the same detection performance as an antenna without a reflector in the area outside the dashed box.

[0146] Figure 8B The simulation results of the antenna without a reflector shown are consistent with... Figure 11A The experimental results shown match those of the antenna without a reflector. Similarly, Figure 9B The simulation results of the prototype machine shown are consistent with Figure 11B The experimental results of the prototype shown match. That is, it can be seen that there is a correlation between the gain obtained through simulation and the detection results of the object obtained through the radio wave sensor.

[0147] The inventors studied the composition (shape, size, and position) of reflective surfaces in various modes.

[0148] Referring to Figure 12 .

[0149] θ1 is an angle that a first straight line 141 connecting the front end of the reflecting surface 131 and the center 140a of the antenna region 125 makes with the antenna surface 120a in a plane perpendicular to the first direction X. The antenna surface 120a is a main surface of the antenna section 120, and is a plane in which the antenna elements 121a, 121b, 121c, 121d, 121e, 121f, 121g are arranged. In Fig. 7, θ2 is an angle that a second straight line 142 connecting the base end of the reflecting surface 131 and the center 140a of the antenna region 125 makes with the antenna surface 120a in a plane perpendicular to the first direction X. θ3 is an angle that the antenna surface 120a makes with the reflecting plate 130 (reflecting surface 131), i.e., an inclination angle of the reflecting plate 130 with respect to the antenna surface 120a.

[0150] The greater the angle θ1, the greater the length of the reflecting surface 131 that protrudes forward. Therefore, the greater the angle θ1, the greater the range of the upwardly directed electric waves reflected by the reflecting surface 131 that becomes directed forward. However, in the case where the reflecting plate 130 is inclined in such a manner that the front end of the reflecting plate 130 is lowered, the greater the angle θ1, the greater the range of the antenna region 125 blocked by the front side portion of the reflecting surface 131, and the greater the range of the electric waves radiated from the antenna region 125 that is blocked forward. The angle θ1 is set in a range exceeding 0° and being less than 90°.

[0151] The smaller the angle θ2, the closer the base end portion of the reflecting surface 131 to the antenna region 125, and the greater the range of the upwardly directed electric waves reflected by the reflecting surface 131 that becomes directed rearward. In other words, the greater the angle θ2, the greater the separation between the reflecting surface 131 and the antenna region 125, and the greater the amount of the electric waves radiated upward through the separation. The angle θ2 is set in a range exceeding 0° and being less than 90°.

[0152] The inventors performed simulation of the directivity of the antenna realized by the electric wave sensor 100 for a plurality of combinations of θ1 and θ2. Note that θ3 was set to 71°.

[0153] Referring to Figure 13A and Figure 13B .

[0154] When Figure 8A is compared with Figure 13A , in the case where θ1 = 80° and θ2 = 25°, a horizontal plane directivity approximately the same as that of the antenna without the reflecting plate is obtained in the front side of the antenna related to the detection of the object (in a range of 90° leftward to 90° rightward with respect to the front direction).

[0155] On the other hand, whenFigure 8B When compared with Figure 13B , in the case of θ1= 80°, θ2= 25°, the gain is improved at 50° to 60° (particularly around 57°) below the antenna without the reflector. On the other hand, in the case of θ1= 80°, θ2= 25°, the gain is reduced in the range of 50° to 90° above. The simulation results in the case of θ1= 80°, θ2= 25° are the same as the simulation results in the above-mentioned trial machine (refer to Figure 9B ). In the case of the reflecting surface of the reflector 130X being θ1= 80°, θ2= 25°, although the reflecting surface is smaller than that of the trial machine, the same good results as the trial machine are obtained.

[0156] Refer to Figure 14A and Figure 14B .

[0157] When Figure 8A is compared with Figure 14A , in the case of θ1= 75°, θ2= 25°, the horizontal plane directivity on the front side of the antenna related to the detection of the object is obtained which is approximately the same as that of the antenna without the reflector.

[0158] With regard to the simulation results shown in Figure 14B , it is considered that although the gain at 50° to 60° below is reduced by about 1 dB compared with the case of θ1= 80°, θ2= 25°, the gain required for the detection of the object can be ensured.

[0159] Refer to Figure 15A and Figure 15B .

[0160] When Figure 8A is compared with Figure 15A , in the case of θ1= 70°, θ2= 25°, the horizontal plane directivity on the front side of the antenna related to the detection of the object is obtained which is approximately the same as that of the antenna without the reflector.

[0161] With regard to the simulation results shown in Figure 15B , the gain at 50° to 60° below is also reduced by 5 dB compared with the case of θ1= 80°, θ2= 25°, which is insufficient for the detection of the object.

[0162] Refer to Figure 16A and Figure 16B .

[0163] When Figure 8A is compared with Figure 16AWhen compared, in the case of θ1= 80°, θ2= 30°, substantially the same horizontal plane directivity as the antenna without the reflecting plate was obtained on the front side of the antenna related to detection of the object.

[0164] With regard to Figure 16B The simulation results shown in FIG. 9 indicate that, although the gain at 50° to 60° below is reduced by about 1 dB compared to the case of θ1= 80°, θ2= 25°, the gain required for detection of the object can be ensured.

[0165] Referring to Figure 17A and Figure 17B .

[0166] When compared with Figure 8A and Figure 17A , in the case of θ1= 80°, θ2= 35°, substantially the same horizontal plane directivity as the antenna without the reflecting plate was obtained on the front side of the antenna related to detection of the object.

[0167] With regard to Figure 17B the simulation results shown in FIG. 10 indicate that, compared to the case of θ1= 80°, θ2= 25°, the gain at 50° to 60° below is also reduced by 5 dB, which is insufficient for detection of the object.

[0168] In summary, if θ1is set to be equal to or greater than 75°, the gain required for detection of the object can be obtained. If θ2is set to be 30° or less, the gain required for detection of the object can be obtained. Therefore, the angle formed by the first straight line 141 connecting the front end of the reflecting surface 131 and the center 140a of the antenna region 125 and the antenna surface 120a in the plane perpendicular to the first direction X can be set to be equal to or greater than 75°. The angle formed by the second straight line 142 connecting the base end of the reflecting surface 131 and the center 140a of the antenna region 125 and the antenna surface 120a in the plane perpendicular to the first direction X can also be set to be 30° or less. If θ1is set to be equal to or greater than 80°, the gain is further improved. Therefore, the angle formed by the first straight line 141 connecting the front end of the reflecting surface 131 and the center 140a of the antenna region 125 and the antenna surface 120a in the plane perpendicular to the first direction X can be set to be equal to or greater than 80°. If θ2is set to be 25° or less, the gain is further improved. Therefore, the angle formed by the second straight line 142 connecting the base end of the reflecting surface 131 and the center 140a of the antenna region 125 and the antenna surface 120a in the plane perpendicular to the first direction X can be set to be equal to or less than 25°.

[0169] In the reflecting surface 131, a reflecting region of an electric wave corresponding to each of the antenna elements 121a, 121b, 121c, 121d, 121e, 121f, and 121g is determined. Referring toFigure 18 .

[0170] In Figure 18 , the reflection region 132a corresponds to the antenna element 121a. That is, the electric wave reflected in the reflection region 132a is received by the antenna element 121a. The reflection region 132b corresponds to the antenna element 121b, and the electric wave reflected in the reflection region 132b is received by the antenna element 121b. The reflection region 132c corresponds to the antenna element 121c, and the electric wave reflected in the reflection region 132c is received by the antenna element 121c. The reflection region 132d corresponds to the antenna element 121d, and the electric wave reflected in the reflection region 132d is received by the antenna element 121d. The reflection region 132e corresponds to the antenna element 121e, and the electric wave irradiated from the antenna element 121e is reflected in the reflection region 132e. The reflection region 132f corresponds to the antenna element 121f, and the electric wave irradiated from the antenna element 121f is reflected in the reflection region 132f. The reflection region 132g corresponds to the antenna element 121g, and the electric wave irradiated from the antenna element 121g is reflected in the reflection region 132g.

[0171] The reflection regions 132a, 132b, 132c, 132d, 132e, 132f, 132g are regions in which the electric wave of a strength sufficient for object detection is reflected, respectively. The reflection regions 132a, 132b, 132c, 132d, 132e, 132f, 132g can each be defined as a region including at least a region in which the strength of the electric wave irradiated from the antenna elements 121a, 121b, 121c, 121d, 121e, 121f, 121g, respectively, is greater than or equal to -3 dB with respect to the peak value of the main lobe.

[0172] The adjacent reflection regions overlap each other in a part. A part of the reflection region 132a overlaps a part of the reflection region 132b. A part of the reflection region 132b overlaps a part of the reflection region 132c. A part of the reflection region 132c overlaps a part of the reflection region 132d. A part of the reflection region 132d overlaps a part of the reflection region 132e. A part of the reflection region 132e overlaps a part of the reflection region 132f. A part of the reflection region 132f overlaps a part of the reflection region 132g.

[0173] The reflection surface 131 can include all of the reflection regions 132a, 132b, 132c, 132d, 132e, 132f, 132g. In this case, the left end of the leftmost reflection region 132a and the right end of the rightmost reflection region 132g are included in the range of the reflection surface 131.

[0174] Referring to Figure 19Here, although the antenna element 121a is described as a representative, the same applies to the antenna elements 121b, 121c, 121d, 121e, 121f, and 121g.

[0175] The antenna element 121a is an array antenna including three elements 122a, 122b, and 122c arranged in the second direction Y. The length (hereinafter also referred to as "element width") X4 of the antenna element 121a in the first direction X is defined by the length of the central element 122b among the elements 122a, 122b, and 122c in the first direction. The element 122b is the element among the elements 122a, 122b, and 122c having the largest length in the first direction X.

[0176] The length of the reflecting surface 131 in the first direction X can be determined based on the element width X4. For example, the length (hereinafter also referred to as "region width") X3 of each of the reflecting regions 132a, 132b, 132c, 132d, 132e, 132f, and 132g in the first direction X can be determined in accordance with the element width X4 (refer to Figure 18 The length of the reflecting surface 131 in the first direction X is determined in such a manner that all of the reflecting regions 132a, 132b, 132c, 132d, 132e, 132f, and 132g are included in the reflecting surface 131.

[0177] Refer to Figure 20 The straight line 123a is a straight line obtained by projecting the center line in the first direction X of the leftmost antenna element 121a to the reflecting surface 131 in a direction perpendicular to the first direction X. The straight line 123g is a straight line obtained by projecting the center line in the first direction X of the rightmost antenna element 121g to the reflecting surface 131 in a direction perpendicular to the first direction X. The reflecting surface 131 includes a region between a straight line 124a that is leftward of the straight line 123a by a length of half the region width X3 and a straight line 124g that is rightward of the straight line 123g by a length of half the region width X3 in the first direction X. That is, the length X1 of the reflecting surface 131 in the first direction X is greater than or equal to the length between the straight line 124a and the straight line 124g, that is, greater than or equal to the length X5 between the left end of the leftmost reflecting region 132a and the right end of the rightmost reflecting region 132g in the first direction X.

[0178] That is, the longer the region width X3, the longer the length X1 of the reflecting surface 131 in the first direction X. If the length X1 of the reflecting surface 131 in the first direction X is made longer, it is possible to suppress the left and right sides of the electric waves radiated upward from the antenna region 125 from escaping from the reflecting surface 131.

[0179] The inventors performed simulation of the directivity of the antenna realized by the electric wave sensor 100 with respect to the region width X3 of the plurality of patterns. Here, the region width X3 is defined as a constant multiple of the element width X4 (X3 = a x X4).

[0180] Referring to Figure 21A and Figure 21B .

[0181] When Figure 8A is compared with Figure 21A , in the case of a = 10, on the front side of the antenna related to detection of the object, substantially the same horizontal plane directivity as the antenna without the reflection plate is obtained.

[0182] When Figure 8B is compared with Figure 21B , in the case of a = 10, the gain is improved at 50° to 60° (particularly, around 57°) lower than the antenna without the reflection plate. In the case of a = 10, in the range of 50° to 90° upward, the gain is reduced compared with the antenna without the reflection plate. The simulation result in the case of a = 10 is the same as the simulation result in the above-described trial-manufactured machine (refer to Figure 9B ). At a = 10, it can be said that the length X1 of the reflection surface 131 in the first direction X is large enough, and a good result is obtained.

[0183] Referring to Figure 22A and Figure 22B .

[0184] When Figure 8A is compared with Figure 22A , in the case of a = 4, on the front side of the antenna related to detection of the object, substantially the same horizontal plane directivity as the antenna without the reflection plate is obtained.

[0185] With respect to the simulation result shown in Figure 22B , it is considered that although the gain at 50° to 60° lower is reduced by about 1 dB compared with the case of a = 10, the gain required for object detection can be ensured.

[0186] Referring to Figure 23A and Figure 23B .

[0187] When Figure 8A is compared with Figure 23A , in the case of a = 1, on the front side of the antenna related to detection of the object, substantially the same horizontal plane directivity as the antenna without the reflection plate is obtained.

[0188] With respect to the simulation result shown in Figure 23BThe simulation results shown indicate that the gain is also reduced by 5 dB at the lower 50° to 60° compared to the case where a = 10, which is insufficient for object detection.

[0189] Referring to Figure 24A and Figure 24B .

[0190] When comparing Figure 8A with Figure 24A , it is understood that even if X3 is changed, the horizontal plane directivity of the front side of the antenna is substantially unchanged, and substantially the same horizontal plane directivity as the antenna without the reflecting plate is obtained.

[0191] With regard to Figure 24B the simulation results shown, the greater X3 is, the more the gain at the lower side increases. However, when a is greater than or equal to 7, the gain is substantially not increased.

[0192] In summary, if a is set to be greater than or equal to 4, the gain required for object detection can be obtained. The region width X3 can be set to be greater than or equal to 4 times the element width X4 of the antenna element. Moreover, when a = 7, the gain is not improved any more, and therefore, the region width X3 can be set to be less than or equal to 7 times the element width X4 of the antenna element.

[0193] [5. Modified example]

[0194] The reflecting plate 130 can also be a reflecting array reflecting plate. By appropriately setting the reflection angle of the electric wave of the reflecting array reflecting plate, the irradiation region 40B (refer to Figure 12 ) of the electric wave reflected by the reflecting plate 130 can be adjusted regardless of the angle (θ3 in Figure 4B ) between the reflecting plate and the antenna face 120a.

[0195] In the above-described embodiment, the reflecting plate 130 is housed in the housing 150, but is not limited thereto. Referring to Figure 25 , in a first modified example shown in Figure 25 , the reflecting plate 130B is disposed outside the housing 150B of the electric wave sensor 100B. Specifically, the reflecting plate 130B is fitted above the transceiving face 151B of the housing 150B. The lower surface of the reflecting plate 130B is the reflecting face 131B. Even with this configuration, a portion of the electric wave irradiated upward from the transceiving face 151B can be reflected downward by the reflecting face 131B of the reflecting plate 130B, and the detection region can be enlarged.

[0196] In the above-described embodiment, the reflecting plate 130 is a flat plate, but is not limited thereto. Referring to Figure 26 , in a second modified example shown in Figure 26In the second modified example of the radio wave sensor 100C shown, the reflector 130C is configured as a bent plate. That is, the reflector 130C includes a first part 133a and a second part 133b. One end of the first part 133a is fixed to the housing 150. The first part 133a and the second part 133b are both flat plates, and a fixed angle of not 0° is provided between the first part 133a and the second part 133b.

[0197] In the second variation, at least one of the first part 133a and the second part 133b is provided with a reflective surface. That is, a reflective surface can be provided on the lower surface of both the first part 133a and the second part 133b, or a reflective surface can be provided only on the lower surface of the first part 133a, or a reflective surface can be provided only on the lower surface of the second part 133b.

[0198] Reference Figure 27 .exist Figure 27 In the third modified example of the radio wave sensor 100D shown, the reflector 130D is configured as a plate bent into an arc shape. For example, the curvature of the reflector 130D can be fixed or the curvature can change midway.

[0199] In the third variation, a reflective surface is provided on at least a portion of the lower surface of the reflector 130D. That is, the reflective surface can be provided on the entire lower surface of the reflector 130D, or only on the front portion of the lower surface of the reflector 130D, or only on the rear portion of the reflector 130D.

[0200] Reference Figure 28 .exist Figure 28 In the fourth modified example of the radio wave sensor 100E shown, the reflector 130E has a shape that is not rectangular but based on the intensity distribution of the radio waves reflected in the reflector 130E. Specifically, the front end of the reflector 130E has a parabolic shape formed by multiple protrusions arranged in the X direction. Each protrusion is... Figure 18 The outer edges of the reflective regions 132a, 132b, 132c, 132d, 132e, 132f, and 132g shown have the same shape. That is, the front end of the reflector 130E has a shape formed by connecting the outer edges of the reflective regions 132a, 132b, 132c, 132d, 132e, 132f, and 132g. Therefore, the reflector 130E can reflect electromagnetic waves of sufficient intensity for object detection, and the reflector 130E can be made small.

[0201] The embodiments disclosed herein are exemplary in all respects and not restrictive. The scope of the invention is set forth not by the above embodiments, but by the claims, including all modifications within the meaning and scope of the claims.

[0202] EXPLANATION OF REFERENCE NUMERALS

[0203] 10: pedestrian signal light

[0204] 20: crosswalk

[0205] 21A, 21B: waiting area

[0206] 30A, 30B: detection area

[0207] 40A, 40B: radio wave irradiation area

[0208] 50: structure

[0209] 60: lane

[0210] 61A, 61B: sidewalk

[0211] 100, 100A, 100B, 100C, 100D, 100E, 100R, 100X: radio wave sensor 110: circuit substrate

[0212] 111: detection processing circuit

[0213] 112: power supply circuit

[0214] 113: interface unit

[0215] 120, 120X: antenna unit

[0216] 120a: antenna surface

[0217] 121a, 121b, 121c, 121d, 121e, 121f, 121g: antenna element

[0218] 122a, 122b, 122c: element

[0219] 123a, 123g, 124a, 124g: straight line

[0220] 125: antenna region

[0221] 130, 130B, 130C, 130D, 130E, 130X: reflection plate

[0222] 131, 131B: reflection surface

[0223] 132a, 132b, 132c, 132d, 132e, 132f, 132g: reflection region

[0224] 133a: first portion

[0225] 133b: second portion;

[0226] 140: center axis;

[0227] 140a: center;

[0228] 141: first straight line;

[0229] 142: second straight line;

[0230] 150, 150B: housing (holding portion);

[0231] 151B: transceiving surface;

[0232] h: height of installation of the radio wave sensor;

[0233] Y1, Y2: distance from the front end of the reflecting surface to the upper end of the antenna region;

[0234] X1: length of the reflecting surface along the first direction;

[0235] X2: length of the antenna region along the first direction;

[0236] X3: length of the reflecting region along the first direction;

[0237] X4: length of the antenna element along the first direction;

[0238] X5: length along the first direction between the left end of the leftmost reflecting region and the right end of the rightmost reflecting region.

Claims

1. An electromagnetic wave sensor, comprising: The antenna section includes multiple antenna elements for transmitting and receiving radio waves; The outer casing houses the antenna section; as well as A reflector having a reflective surface that reflects a portion of the radio waves transmitted or received through the antenna section. The antenna section has an antenna region serving as an area for configuring the plurality of antenna elements and for transmitting and receiving the radio waves. The reflector is configured with its reflective surface facing downwards. When viewed from the front, the front end of the reflective surface is positioned above the center of the antenna region.

2. The radio wave sensor according to claim 1, wherein, The front end of the reflective surface is located above the upper end of the antenna region.

3. The radio wave sensor according to claim 1 or 2, wherein, The antenna section also has an antenna surface, which is a plane in which the plurality of antenna elements are arranged in a first direction, which is the horizontal direction. In a plane perpendicular to the first direction, the angle between the first straight line connecting the front end of the reflective surface and the center of the antenna region and the antenna surface is greater than or equal to 75°.

4. The radio wave sensor according to claim 3, wherein, In a plane perpendicular to the first direction, the angle between the second straight line connecting the base end of the reflective surface and the center of the antenna region and the antenna surface is less than or equal to 30°.

5. The radio wave sensor according to any one of claims 1 to 4, wherein, The angle between the reflective surface and the antenna surface is in the range of 60° to 90°.

6. The radio wave sensor according to any one of claims 1 to 5, wherein, The length of the reflective surface along the first direction is greater than or equal to the length of the antenna region along the first direction.

7. The radio wave sensor according to claim 6, wherein, The length of the reflective surface along the first direction is the length of a plurality of defined reflective regions for each of the plurality of antenna elements.

8. The radio wave sensor according to claim 7, wherein, The length of the reflective region along the first direction is greater than or equal to four times the length of the antenna element in the first direction.

9. The radio wave sensor according to claim 7 or 8, wherein, The reflection region includes an area where the intensity of the radio waves irradiated from the antenna element is greater than or equal to -3 dB relative to the peak intensity of the main lobe.

10. The radio wave sensor according to any one of claims 1 to 9, wherein, The radio wave sensor also includes a holding part for holding the antenna part, and the reflector is mounted on the holding part.

11. The radio wave sensor according to any one of claims 1 to 10, wherein, The outer casing houses the reflector.

12. The radio wave sensor according to any one of claims 1 to 11, wherein, The reflector is a rectangular flat plate.

13. The radio wave sensor according to any one of claims 1 to 11, wherein, The reflector is a plate-shaped plate with a bent portion in a direction away from the antenna portion. The reflector includes a first portion closer to the antenna portion than the bent portion and a second portion farther away from the antenna portion than the bent portion. The angle between the second part and the antenna surface is smaller than the angle between the first part and the antenna surface.

14. The radio wave sensor according to any one of claims 1 to 4 and claims 6 to 11, wherein, The reflector is a plate-shaped structure that is bent with its front end lowered.

15. The radio wave sensor according to any one of claims 1 to 14, wherein, The front end of the reflector has a shape based on the intensity distribution of the electromagnetic waves reflected on the reflective surface.

16. The radio wave sensor according to any one of claims 1 to 15, wherein, The reflective surface illuminates the reflected wave obtained by reflecting the radio wave into the second illumination range, wherein the second illumination range is the illumination range closer to the radio wave sensor compared to the first illumination range that is not reflected by the reflective surface and is irradiated from the antenna to the ground.

17. An electromagnetic wave sensor, comprising: The antenna section includes multiple antenna elements for transmitting and receiving radio waves; The outer casing houses the antenna section; as well as A reflector that reflects a portion of the radio waves transmitted or received through the antenna. The reflector is configured with its reflective surface facing downwards to reflect the radio waves. The front end of the reflective surface is located above the central axis of the main lobe illuminated from the antenna section.

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