Classifications

• • G—PHYSICS
  • G01—MEASURING; TESTING
  • G01S—RADIO DIRECTION-FINDING; RADIO NAVIGATION; DETERMINING DISTANCE OR VELOCITY BY USE OF RADIO WAVES; LOCATING OR PRESENCE-DETECTING BY USE OF THE REFLECTION OR RERADIATION OF RADIO WAVES; ANALOGOUS ARRANGEMENTS USING OTHER WAVES
  • G01S13/00—Systems using the reflection or reradiation of radio waves, e.g. radar systems; Analogous systems using reflection or reradiation of waves whose nature or wavelength is irrelevant or unspecified
  • G01S13/88—Radar or analogous systems specially adapted for specific applications
  • G01S13/91—Radar or analogous systems specially adapted for specific applications for traffic control
• • G—PHYSICS
  • G01—MEASURING; TESTING
  • G01S—RADIO DIRECTION-FINDING; RADIO NAVIGATION; DETERMINING DISTANCE OR VELOCITY BY USE OF RADIO WAVES; LOCATING OR PRESENCE-DETECTING BY USE OF THE REFLECTION OR RERADIATION OF RADIO WAVES; ANALOGOUS ARRANGEMENTS USING OTHER WAVES
  • G01S7/00—Details of systems according to groups G01S13/00, G01S15/00, G01S17/00
  • G01S7/02—Details of systems according to groups G01S13/00, G01S15/00, G01S17/00 of systems according to group G01S13/00
  • G01S7/03—Details of HF subsystems specially adapted therefor, e.g. common to transmitter and receiver
• • H—ELECTRICITY
  • H01—ELECTRIC ELEMENTS
  • H01Q—ANTENNAS, i.e. RADIO AERIALS
  • H01Q19/00—Combinations of primary active antenna elements and units with secondary devices, e.g. with quasi-optical devices, for giving the antenna a desired directional characteristic
  • H01Q19/10—Combinations of primary active antenna elements and units with secondary devices, e.g. with quasi-optical devices, for giving the antenna a desired directional characteristic using reflecting surfaces
• • H—ELECTRICITY
  • H01—ELECTRIC ELEMENTS
  • H01Q—ANTENNAS, i.e. RADIO AERIALS
  • H01Q21/00—Antenna arrays or systems
  • H01Q21/06—Arrays of individually energised antenna units similarly polarised and spaced apart
  • H01Q21/08—Arrays of individually energised antenna units similarly polarised and spaced apart the units being spaced along or adjacent to a rectilinear path

Definitions

• Radio wave sensors for traffic monitoring detect objects (vehicles, pedestrians, etc.) within a detection area set on the road.
• Radio wave sensors are installed at a high location, such as near the top of a pillar, with the radio wave irradiation surface facing diagonally downward so that they irradiate radio waves into the detection area in front, but the area directly below the radio wave sensor is prone to becoming a blind spot. Due to restrictions on where the radio wave sensor can be installed, there are cases where it is required to include the area directly below the radio wave sensor in the detection area.
• Patent Document 1 discloses a radio wave sensor that includes a transmitter capable of transmitting radio waves from a first antenna with an irradiation range limited to a first area, which is an area at the beginning of a crosswalk and does not include the entire crosswalk, a receiver that receives radio waves from the first area, and a detector that detects objects in the first area based on the radio waves received by the receiver.
• the transmitter of the radio wave sensor disclosed in Patent Document 1 is further capable of transmitting radio waves from a second antenna with an irradiation range limited to a second area that includes a portion of the crosswalk that is farther from the radio wave sensor than the first area, the receiver further receives radio waves from the second area, and the detector further detects objects in the second area based on the radio waves from the second area received by the receiver.
• a radio wave sensor comprises an antenna section including a plurality of antenna elements for transmitting and receiving radio waves, a housing for accommodating the antenna section, and a reflector having a reflective surface for reflecting a portion of the radio waves transmitted or received by the antenna section, the antenna section having an antenna area in which the plurality of antenna elements are arranged and which is an area for transmitting and receiving the radio waves, the reflector being arranged so that the reflective surface faces downward, and when the antenna area is viewed from the front, the front end of the reflective surface is located above the center of the antenna area.
• the present disclosure also includes an antenna reflector having the configuration included in the radio wave sensor.
• FIG. 1 is a diagram showing an example of use of a radio wave sensor according to an embodiment.
• FIG. 2 is a perspective view illustrating an example of the configuration of the radio wave sensor according to the embodiment.
• FIG. 3 is a perspective view illustrating an example of an internal configuration of the radio wave sensor according to the embodiment.
• FIG. 4A is a diagram for explaining an example of a radio wave irradiation range of a radio wave sensor that is not provided with a reflector.
• FIG. 4B is a diagram for explaining an example of a radio wave irradiation range of the radio wave sensor according to the embodiment.
• FIG. 5A is a side view of a circuit board and a reflector, showing an example of the positional relationship between the antenna area and the reflecting surface.
• FIG. 5B is a side view of the circuit board and the reflector, showing another example of the positional relationship between the antenna area and the reflecting surface.
• FIG. 5C is a side view of the circuit board and the reflector, showing yet another example of the positional relationship between the antenna region and the reflecting surface.
• FIG. 6 is a perspective view of a circuit board and a reflector, showing an example of the positional relationship between the antenna area and the reflecting surface in the first direction X.
• FIG. 7A is a perspective view showing the configuration of an antenna with a reflector used in the simulation.
• FIG. 7B is a front view showing the configuration of an antenna with a reflector used in the simulation.
• FIG. 7C is a side view showing the configuration of the antenna with a reflector used in the simulation.
• FIG. 8A is a graph showing the simulation results of the horizontal plane directivity of an antenna without a reflector.
• FIG. 8B is a graph showing the simulation results of the vertical plane directivity of an antenna without a reflector.
• FIG. 9A is a graph showing the simulation results of the horizontal plane directivity of an antenna with a reflector.
• FIG. 9B is a graph showing the simulation results of the vertical plane directivity of an antenna with a reflector.
• FIG. 10 is a diagram showing the walking patterns of subjects in a performance evaluation experiment.
• FIG. 11A is a graph showing the results of an experiment evaluating the performance of an antenna without a reflector.
• FIG. 11B is a graph showing the results of a performance evaluation experiment of an antenna with a reflector fabricated to have the antenna directivity shown in FIGS. 9A and 9B.
• FIG. 12 is a side view of the circuit board and the reflector for explaining the setting of the positions of the front end and the base end of the reflecting surface.
• FIG. 18 is a diagram for explaining a reflection area on a reflection surface.
• FIG. 19 is a front view showing the configuration of one antenna element.
• FIG. 20 is a diagram showing an example of setting the length of the reflecting surface in the first direction.
• FIG. 24A is a graph showing the simulation results of horizontal plane directivity when X3 is changed in 1 mm intervals in the range from 1 to 20 mm.
• FIG. 24B is a graph showing the simulation results of the vertical directivity when X3 is changed in 1 mm intervals in the range from 1 to 20 mm.
• FIG. 25 is a perspective view showing a first modified example of the radio wave sensor according to the embodiment.
• FIG. 26 is a perspective view showing a second modified example of the radio wave sensor according to the embodiment.
• FIG. 27 is a perspective view showing a third modified example of the radio wave sensor according to the embodiment.
• FIG. 28 is a perspective view showing a fourth modified example of the radio wave sensor according to the embodiment.
• the detection area of a radio wave sensor can be expanded without increasing the number of antennas.
• the radio wave sensor comprises an antenna section including a plurality of antenna elements that transmit and receive radio waves, a housing that accommodates the antenna section, and a reflector having a reflective surface that reflects a portion of the radio waves transmitted or received by the antenna section, the antenna section having an antenna area in which the plurality of antenna elements are arranged and which transmits and receives the radio waves, the reflector being arranged so that the reflective surface faces downward, and when the antenna area is viewed from the front, the front end of the reflective surface is located above the center of the antenna area.
• the front end of the reflector may be located above the upper end of the antenna area. This can further reduce the blocking of the main lobe radiated from the antenna unit.
• the antenna unit may further have an antenna surface that is a plane on which the multiple antenna elements are arranged in a first direction that is a horizontal direction, and in a plane perpendicular to the first direction, an angle between the antenna surface and a first line connecting the front end of the reflecting surface and the center of the antenna area may be 75° or more. This allows the front end of the reflector to be located in a range where radio wave intensity is high, improving the gain below the antenna unit.
• the angle between the antenna surface and a second straight line connecting the base end of the reflector and the center of the antenna area may be 30° or less. This allows the base end portion of the reflector to be located in a range of high radio wave intensity, improving the gain below the antenna unit.
• the “base end” is the end opposite the front end. Specifically, the “base end” is the end at which the reflector is attached to a base member (e.g., a housing) that serves as a base for supporting the reflector.
• the angle between the reflecting surface and the antenna surface may be in the range of 60° to 90°. This allows the radio waves to be reflected to a position closer to the radio wave sensor, thereby expanding the detection area.
• the length of the reflecting surface along the first direction may be equal to or greater than the length of the antenna region along the first direction. This allows a large portion of the side lobes heading upward to be reflected.
• the length of the reflective surface along the first direction may be a length that includes a plurality of reflective areas defined for each of the plurality of antenna elements. This allows radio waves radiated from each antenna element to be reflected by the reflector, thereby improving the gain of the antenna.
• the length of the reflective area along the first direction may be four or more times the length of the antenna element in the first direction. This allows the reflector to be positioned in a range where the radio wave intensity is high in the first direction, improving the gain below the antenna unit.
• the reflection area may include an area where the strength of the radio waves irradiated from the antenna element is -3 dB or more relative to the peak radio wave strength of the main lobe. This allows radio waves of sufficient strength (-3 dB or more) to be reflected without leakage, improving the gain below the antenna unit.
• a holder for holding the antenna unit may be further provided, and the reflector may be attached to the holder. This allows the reflector to be positioned close to the antenna unit, and reduces errors in the attachment position of the reflector relative to the antenna unit.
• the housing may house the reflector. This can protect the reflector from wind and rain, and can prevent the reflector from shifting out of position.
• the reflector may be a rectangular flat plate. This simplifies the configuration of the reflector.
• the reflector may be plate-shaped with a bent portion in a part of the direction away from the antenna unit, and may include a first portion closer to the antenna unit than the bent portion and a second portion farther from the antenna unit than the bent portion, and the angle between the second portion and the front antenna surface may be smaller than the angle between the first portion and the antenna surface. This allows the detection area to be expanded to a position closer to the radio wave sensor.
• the reflector may be a plate-like shape curved with a downwardly-inclined front end. This allows the detection area to be expanded to a position closer to the radio wave sensor.
• the front end of the reflector may have a shape based on the intensity distribution of the radio waves reflected by the reflecting surface. This allows a small reflector to be constructed while ensuring high radio wave intensity.
• the reflecting surface may irradiate a reflected wave that reflects the radio wave to a second irradiation range that is closer to the radio wave sensor than a first irradiation range that is irradiated from the antenna unit to the ground without being reflected by the reflecting surface. This makes it possible to expand the detection area to a position closer to the radio wave sensor.
• the radio wave sensor comprises an antenna section including multiple antenna elements that transmit and receive radio waves, a housing that accommodates the antenna section, and a reflector that reflects a portion of the radio waves transmitted or received by the antenna section, the reflector being positioned so that the reflective surface that reflects the radio waves faces downward, and the front end of the reflector being positioned above the central axis of the main lobe radiated from the antenna section.
• a radio wave sensor 100 is a radio wave radar for traffic monitoring, and detects pedestrians on a crosswalk 20.
• the radio wave sensor 100 is attached to a structure 50 provided on the sidewalk 61B.
• the structure 50 is several meters high, and the radio wave sensor 100 is installed several meters above the ground.
• the radio wave sensor 100 detects objects (e.g., pedestrians, bicycles, vehicles) on the crosswalk 20 by emitting radio waves (millimeter waves) onto the crosswalk 20 and receiving the reflected waves. More specifically, the radio wave sensor 100 can detect the distance from the radio wave sensor 100 to an object on the crosswalk 20, the speed of the object, and the horizontal angle (hereinafter referred to as the "azimuth angle") of the object's location relative to the radio wave emission axis (the central axis of the main lobe).
• objects e.g., pedestrians, bicycles, vehicles
• the radio wave sensor 100 can detect the distance from the radio wave sensor 100 to an object on the crosswalk 20, the speed of the object, and the horizontal angle (hereinafter referred to as the "azimuth angle") of the object's location relative to the radio wave emission axis (the central axis of the main lobe).
• the radio wave sensor 100 is equipped with a reflector 130 as described below, and detects objects using millimeter waves reflected by the reflector 130.
• the path length of the radio waves increases.
• the increase in the path length of the radio waves caused by the reflector 130 is within the margin of error, and detection accuracy does not substantially decrease.
• Passersby include pedestrians and bicycles (specifically, bicycles with a passenger on board).
• the radio wave sensor 100 detects the passersby and their positions (distance and azimuth) and speed.
• the radio wave sensor 100 includes a circuit board 110, a reflector 130, and a housing 150.
• the circuit board 110 and the reflector 130 are housed in the housing 150.
• the housing 150 is an example of a "housing section.”
• the circuit board 110 includes an antenna section 120.
• the housing 150 has an external shape, for example, a rectangular parallelepiped, one side of which is a surface for transmitting and receiving radio waves.
• FIG. 3 shows the circuit board 110 and the reflector 130.
• the circuit board 110 is flat.
• one direction along the main surface of the circuit board 110 is referred to as the first direction X.
• a direction along the main surface of the circuit board 110 that is perpendicular to the first direction X is referred to as the second direction Y.
• a direction perpendicular to the first direction X and the second direction Y is 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 transmitting/receiving surface of the housing 150.
• the radio wave sensor 100 is installed so that the second direction Y is the upward direction. If the first end of the circuit board 110 in the second direction Y (the end closest to the reflector 130 in FIG. 3) is located on the upper side and the second end of the circuit board 110 in the second direction Y (the end farther from the reflector 130 in FIG. 3) is located on the lower side, the front of the housing 150 of the radio wave sensor 100 may be inclined downward.
• the second direction Y is also referred to as "upward” and the opposite side of the second direction Y is also referred to as “downward”.
• the first direction X is also referred to as "leftward” and the opposite side of the first direction X is also referred to as "rightward”.
• the third direction Z is also referred to as "forward” and the opposite side of the third direction Z is also referred to as "rearward”.
• the circuit board 110 includes a detection 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 each of the antenna section 120, the detection processing circuit 111, the power supply circuit 112, and the interface section 113 is configured as a partial circuit of the circuit board 110.
• 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 radiate (transmit) radio waves, and the receiving antenna elements 121a, 121b, 121c, and 121d receive the radio waves.
• the antenna unit 120 is, for example, an array antenna.
• the receiving antenna elements 121a, 121b, 121c, and 121d form an array antenna for reception
• the transmitting antenna elements 121e, 121f, and 121g form an array antenna for transmission.
• the "receiving antenna elements” and “transmitting antenna elements” are also referred to as “antenna elements.”
• antenna elements 121a, 121b, 121c, 121d, 121e, 121f, and 121g are arranged in a horizontal row.
• Receiving antenna elements 121a, 121b, 121c, and 121d are arranged in a horizontal row, and transmitting antenna elements 121e, 121f, and 121g are also arranged in a horizontal row.
• the antenna section 120 includes an antenna area 125 that includes receiving antenna elements 121a, 121b, 121c, and 121d and transmitting antenna elements 121e, 121f, and 121g.
• the antenna area 125 is an area in which the antenna section 120 transmits and receives radio waves.
• the receiving antenna elements 121a, 121b, 121c, and 121d and the transmitting antenna elements 121e, 121f, and 121g are configured on the surface of the circuit board 110. Therefore, the antenna area 125 is an area on the XY plane.
• the left end of antenna region 125 coincides with the left end of antenna element 121a, which is the leftmost of antenna elements 121a, 121b, 121c, 121d, 121e, 121f, and 121g.
• the right end of antenna region 125 coincides with the right end of antenna element 121g, which is the rightmost of antenna elements 121a, 121b, 121c, 121d, 121e, 121f, and 121g.
• the top end of antenna region 125 coincides with the top end of antenna element 121f, which is the topmost of antenna elements 121a, 121b, 121c, 121d, 121e, 121f, and 121g.
• antenna region 125 coincides with the bottom ends of antenna elements 121a, 121b, 121c, 121d, 121e, and 121g.
• antenna region 125 is the rectangular region of the smallest area that surrounds antenna elements 121a, 121b, 121c, 121d, 121e, 121f, and 121g.
• the detection processing circuit 111 generates a modulated wave.
• the generated modulated wave is transmitted from the transmitting antenna elements 121e, 121f, and 121g.
• the transmitted modulated wave hits an object (e.g., a pedestrian, a bicycle, or a vehicle) and is reflected.
• receiving antenna elements 121a, 121b, 121c, and 121d are used to detect the azimuth angle of an object.
• 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, and detects the position (distance and azimuth angle) and speed of the object.
• the interface unit 113 is a circuit for communicating with an external device.
• the interface unit 113 includes a connector (not shown) and can be connected to an external device via a cable.
• the interface unit 113 can transmit detection result data to the connected external device.
• the interface unit 113 may be a wireless communication interface and can communicate with an external device wirelessly.
• the power supply circuit 112 supplies power to the detection processing circuit 111.
• a reflector 130 is disposed above the circuit board 110.
• the reflector 130 is, for example, a rectangular flat plate.
• the circuit board 110 and the reflector 130 are attached 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 reflector 130 is attached to the holding portion.
• the mounting structure of the circuit board 110 and the reflector 130 is not limited to this.
• the circuit board 110 and the reflector 130 may be attached to a holding member fixed to the inner surface of the housing 150.
• the reflector 130 includes a reflecting surface 131 (see FIG. 4B) for reflecting radio waves.
• the reflecting surface 131 is positioned so as to reflect a portion of the radio waves transmitted from the antenna unit 120.
• the reflecting surface 131 faces diagonally downward, and reflects radio waves toward the road diagonally below the radio wave sensor 100, primarily toward the roadway 60 and sidewalk 61A in the example of FIG. 1.
• Reflective surface 131 is provided on the underside of reflector 130.
• reflector 130 is made of metal.
• the underside of reflector 130 is reflective surface 131.
• reflector 130 may be made of a metal plate attached to the underside of a holding plate made of synthetic resin, for example. In this case, the underside of the metal plate is reflective surface 131.
• detection areas 30A and 30B are set as ranges on a road for detecting an object.
• the detection areas 30A and 30B are set as parts of radio wave irradiation areas 40A and 40B of the radio wave sensor 100.
• the radio wave irradiation area 40A is the range where radio waves are directly irradiated from the antenna unit 120 of the radio wave sensor 100.
• the radio wave irradiation area 40B is the range where radio waves transmitted from the antenna unit 120 of the radio wave sensor 100 and reflected by the reflector 130 are irradiated.
• detection area 30A is set inside radio wave irradiation area 40A.
• Detection area 30B is set inside radio wave irradiation area 40B.
• Pedestrian waiting areas 21A, 21B are provided at both ends of the crosswalk 20 where it is connected to the sidewalks 61A, 61B.
• the waiting areas 21A, 21B are set up on the sidewalks 61A, 61B provided on both sides of the roadway 60.
• pedestrians wait for the pedestrian traffic light 10 to change from red (no passage) to green (permitted passage).
• the structure 50 on which the radio wave sensor 100 is attached is installed, for example, on sidewalk 61B, which is one of the sidewalks 61A, 61B on both sides of the roadway 60.
• the waiting area 21A provided on sidewalk 61A on which the radio wave sensor 100 is not installed is referred to as the "first waiting area 21A”
• the waiting area 21B provided on sidewalk 61B on which the radio wave sensor 100 is installed is referred to as the "second waiting area 21B.”
• the detection area 30A is an area that includes the crosswalk 20 and the first waiting area 21A.
• the detection area 30B is an area that includes 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.
• Radio waves are emitted radially from the radio wave sensor 100A.
• the installation angle of the radio wave sensor 100A is adjusted so that the radio wave emission axis can detect the first waiting area 21A of the sidewalk 61A without omission and faces downward as much as possible.
• the radio wave emission axis passes through the center of the transmission/reception surface and is perpendicular to the transmission/reception surface.
• the radio wave emission axis has the highest gain in the directivity of the plane perpendicular to the transmission/reception surface (the YZ plane in Figure 4A).
• the radio wave sensor 100A is installed on the sidewalk 61B.
• the radio wave sensor 100A is not installed on the sidewalk 61A on the opposite side of the roadway 60 from the sidewalk 61B. A part of the radio waves is emitted diagonally upward from the radio wave sensor 100A installed in this way.
• the height of the pedestrian (or vehicle) on the crosswalk 20 is the object to be detected, and is within a range of h or less from the ground of the pedestrian (or vehicle). Therefore, the radio wave sensor 100A only needs to be able to detect objects at a height of h or less. In other words, radio waves irradiated above a height h are not used for object detection.
• a second waiting area 21B is set from the boundary between the crosswalk 20 and the sidewalk 61B in a direction closer to the radio wave sensor 100A (structure 50), with a width of, for example, 2m or more (see Figure 1).
• the distance from the end of the second waiting area 21B of the sidewalk 61B where the radio wave sensor 100 is installed that is closest to the structure 50 to the installation position of the structure 50 is called the "setback.”
• the setback must be greater than the width of the second waiting area 21B.
• the setback must be 2m or more.
• the radio wave sensor 100A that does not have a reflector 130, unless the setback is made sufficiently large, it will not be possible to irradiate radio waves of a sufficiently high intensity to the second waiting area 21B. This may result in reduced accuracy in detecting objects in the second waiting area 21B. Depending on the layout of the sidewalk 61B on which the radio wave sensor 100A is installed, it may be difficult to ensure a large setback. This limits the freedom of installation of the radio wave sensor 100A. In contrast, with the radio wave sensor 100 that has a reflector 130, it is possible to irradiate radio waves of a sufficiently high intensity to the second waiting area 21B without making the setback large. This improves the freedom of installation of the radio wave sensor 100.
• the transmitting antenna elements 121e, 121f, and 121g transmit radio waves toward the detection area 30A.
• the receiving antenna elements 121a, 121b, 121c, and 121d receive the reflected waves that are the radio waves reflected by an object in the detection area 30A.
• the reflected waves that are reflected by an object in the detection area 30A and received directly (without going through the reflector 130) by the receiving antenna elements 121a, 121b, 121c, and 121d are also referred to as "directly reflected waves.”
• radio waves transmitted from the transmitting antenna elements 121e, 121f, and 121g travel toward the reflector 130.
• the radio waves reflected by the reflector 130 are irradiated toward the detection area 30B.
• the receiving antenna elements 121a, 121b, 121c, and 121d receive the reflected waves, which are radio waves reflected by an object in the detection area 30B, via the reflector 130.
• the reflected waves reflected by an object in the detection area 30B and received by the receiving element antennas 121a, 121b, 121c, and 121d via the reflector 130 are also referred to as "indirectly reflected waves.”
• a portion of the radio waves emitted upward from the radio wave sensor 100 is reflected by the reflector 130 and irradiated to the ground.
• the radio waves emitted upward are not used to detect objects.
• by reflecting the radio waves emitted upward by the reflector 130 and irradiating them to the ground they can be used to detect objects.
• the irradiation area 40B of the radio waves reflected by the reflector 130 is closer to the radio wave sensor 100 than the radio wave irradiation area 40A. Therefore, even if the setback is small, radio waves can be irradiated to the second waiting area 21B.
• the antenna region 125 is a partial region of the surface of the antenna section 120, but in FIG. 5A, the antenna region 125 is indicated by a thick solid line for ease of understanding.
• the front end of the reflective surface 131 is located above the center of the antenna region 125.
• the central axis 140 is imagined to extend from the center 140a of the antenna region 125 in 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.
• 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 and the upper end of the antenna area 125 are separated by a distance Y1 in the vertical direction.
• the central axis 140 is the radio wave irradiation axis.
• a main lobe is emitted from the antenna area 125 along the central axis 140. Therefore, most of the main lobe is not blocked by the reflecting surface 131.
• the front end of the reflecting surface 131 is located above the center of the antenna region 125
• the portion of the reflecting surface 131 that corresponds to the central axis 140 of the antenna region 125 in the X direction is located above the central axis 140.
• the central axis 140 does not overlap with the reflecting surface 131, so most of the main lobe is not blocked by the reflecting surface 131.
• the central axis 140 is the central axis of the main lobe.
• the front end of the reflecting surface 131 is located above the central axis of the main lobe.
• the central axis of the main lobe may be different from the central axis 140 of the antenna region 125.
• the main lobe may be emitted from the antenna region 125 in a direction that is inclined downward by beamforming.
• the central axis of the main lobe extends in a direction different from the normal direction of the antenna region 125.
• the reflector 130 may be tilted so that its front end is lowered. However, as in the example of FIG. 5A, it is required that the central axis 140 is positioned below the front end of the reflecting surface 131.
• the front end of the reflecting surface 131 is located above the upper end of the antenna region 125.
• the front end of the reflecting surface 131 and the upper end of the antenna region 125 are separated by a distance Y2 in the vertical direction. Therefore, even in the example of FIG. 5B, most of the main lobe is not blocked by the reflecting surface 131.
• the front end of the reflecting surface 131 is located above the central axis 140 of the antenna area 125, but below the upper end of the antenna area 125. Even with this configuration, only an upper portion of the main lobe is blocked by the reflecting surface 131, ensuring a sufficient range of the main lobe.
• the front end of the reflecting surface 131 it is undesirable for the front end of the reflecting surface 131 to be located below the center of the antenna area 125. If the reflecting surface 131 is provided in such an area, a large portion of the main lobe will be reflected by the reflecting surface 131, reducing the gain of the radio wave sensor.
• X1 is the length of the reflecting surface 131 along the first direction X
• X2 is the length of the antenna area 125 along the first direction.
• the antenna elements 121a, 121b, 121c, 121d, 121e, 121f, and 121g are aligned along the first direction X (see FIG. 3). Therefore, X1 is the length of the reflecting surface 131 in the first direction X, which is the alignment 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.
• the length X1 of the reflecting surface 131 is longer than the length X2 of the antenna area 125. This allows most of the radio waves traveling upward from the antenna area 125 to be reflected by the reflecting surface 131.
• the inventors created models of an antenna with a reflector and an antenna without a reflector on a computer and performed a simulation of the antenna directivity.
• the width of the reflector 130X is 70 mm, and the length in the vertical direction of the reflector 130X is 25 mm.
• the entire lower surface of the reflector 130X is a reflecting surface.
• the width of the antenna unit 120X is 47 mm, and the height of the antenna unit 120X is 8 mm.
• the base end of the reflector 130X is in contact with the upper end of the antenna unit 120X, and the angle (YZ plane angle) between the reflector 130X and the antenna unit 120X is 71°.
• the size and angle of the reflector 130X are determined so that the front end of the reflector 130X is located above the center of the antenna area when the antenna area of the antenna unit 120X is viewed from the front.
• the angle between the reflector 130X and the antenna unit 120X may be set in the range of 60° to 90°. This allows the reflected wave to be irradiated to an area close to the antenna.
• Figures 8A and 8B Please refer to Figures 9A and 9B.
• the radius indicates the gain (dBi) and the deviation angle indicates the angle around center 140a in the XY plane (the direction of central axis 140 is set to 0°).
• the radius indicates the gain (dB) and the deviation angle indicates the angle around center 140a in the YZ plane (the direction of central axis 140 is set to 0°). The same applies to the following graphs.
• the prototype has improved gain in the range of 50° to 60° below (especially around 57°) compared to the antenna without a reflector.
• the prototype has reduced gain in the range of 50° to 90° above compared to the antenna without a reflector. This increase or decrease in gain is due to the provision of reflector 130X.
• the decrease in gain in the upward range of 50° to 90° is believed to be due to radio waves heading in this range being reflected by reflector 130X.
• the increase in gain in the downward range of 50° to 60° is believed to be due to radio waves in the upward range of 50° to 90° being reflected by reflector 130X toward the downward range of 50° to 60°.
• a subject walking in the pattern shown in Figure 10 was detected by the antenna without a reflector and the prototype.
• the walking pattern was such that from directly below the radio wave sensor 100, the subject walked 7 m forward (in the Z1 direction, which is the direction in which the Z direction is projected onto the ground), then walked 2 m to the right (in the X direction), then walked 7 m backward, and then walked 2 m to the right.
• the pedestrian started walking in the Z1 direction from a position (0,0) (unit: m) where (Z1,X) relative to the radio wave sensor was, and when he reached position (7,0), he changed his direction of travel to the X direction, when he reached position (7,2), he changed his direction of travel to the -Z1 direction, when he reached position (0,2), he changed his direction of travel to -X, and returned to position (0,0).
• the subject walked in the above-mentioned pattern in relation to radio wave sensor 100R equipped with an antenna without a reflector and radio wave sensor 100X equipped with a prototype antenna with a reflector, the subject's position was detected by each of radio wave sensors 100R and 100X.
• FIGS 11A and 11B Each of Figures 11A and 11B shows superimposed detection results output by each of the radio wave sensors 100R and 100X at a predetermined period.
• the vertical axis indicates the distance in the Z1 direction from the radio wave sensors 100R and 100X
• the horizontal axis indicates the distance in the X direction from the radio wave sensors 100R and 100X.
• the antenna without a reflector cannot detect the subject within a range of 3 m forward from the radio wave sensor 100R.
• the prototype can detect the subject even within a range of 3 m forward from the radio wave sensor 100X. It can be seen that the prototype has detection performance equivalent to that of the antenna without a reflector even in areas other than the dashed frame.
• the simulation results of the antenna without a reflector shown in Figure 8B are consistent with the experimental results of the antenna without a reflector shown in Figure 11A.
• the simulation results of the prototype shown in Figure 9B are consistent with the experimental results of the prototype shown in Figure 11B.
• the gain obtained by the simulation is correlated with the object detection results by the radio wave sensor.
• the inventors investigated the configurations (shape, size, and position) of the reflective surface in various patterns.
• ⁇ 1 is the angle between the antenna surface 120a and a first straight line 141 that connects the front end of the reflecting surface 131 and the center 140a of the antenna area 125 in a plane perpendicular to the first direction X.
• the antenna surface 120a is the main surface of the antenna unit 120, and is a plane on which the antenna elements 121a, 121b, 121c, 121d, 121e, 121f, and 121g are arranged.
• ⁇ 2 is the angle between the antenna surface 120a and a second straight line 142 that connects the base end of the reflecting surface 131 and the center 140a of the antenna area 125 in a plane perpendicular to the first direction X.
• ⁇ 3 is the angle between the antenna surface 120a and the reflector 130 (reflecting surface 131), i.e., the inclination angle of the reflector 130 with respect to the antenna surface 120a.
• the angle ⁇ 1 is set in the range greater than 0° and less than 90°.
• the angle ⁇ 2 is set in the range greater than 0° and less than 90°.
• the inventors performed a simulation of the antenna directivity of the radio wave sensor 100 for multiple combinations of ⁇ 1 and ⁇ 2. ⁇ 3 was set to 71°.
• the gain required for object detection can be obtained. If ⁇ 2 is set to 30° or less, the gain required for object detection can be obtained. Therefore, in a plane perpendicular to the first direction X, the angle between the first straight line 141 connecting the front end of the reflecting surface 131 and the center 140a of the antenna area 125 and the antenna surface 120a may be set to 75° or more. In a plane perpendicular to the first direction X, the angle between the second straight line 142 connecting the base end of the reflecting surface 131 and the center 140a of the antenna area 125 and the antenna surface 120a may be set to 30° or less. If ⁇ 1 is set to 80° or more, the gain is further improved.
• the angle between the first straight line 141 connecting the front end of the reflecting surface 131 and the center 140a of the antenna area 125 and the antenna surface 120a may be set to 80° or more. If ⁇ 2 is set to 25° or less, the gain is further improved. Therefore, in a plane perpendicular to the first direction X, the angle between the second straight line 142 connecting the base end of the reflecting surface 131 and the center 140a of the antenna area 125 and the antenna surface 120a may be set to 25° or less.
• a radio wave reflecting area corresponding to each of the antenna elements 121a, 121b, 121c, 121d, 121e, 121f, and 121g is determined. See FIG. 18.
• reflection area 132a corresponds to antenna element 121a. That is, the radio waves reflected at reflection area 132a are received by antenna element 121a.
• Reflection area 132b corresponds to antenna element 121b, and the radio waves reflected at reflection area 132b are received by antenna element 121b.
• Reflection area 132c corresponds to antenna element 121c, and the radio waves reflected at reflection area 132c are received by antenna element 121c.
• Reflection area 132d corresponds to antenna element 121d, and the radio waves reflected at reflection area 132d are received by antenna element 121d.
• Reflection area 132e corresponds to antenna element 121e, and the radio waves irradiated from antenna element 121e are reflected at reflection area 132e.
• Reflection area 132f corresponds to antenna element 121f, and the radio waves irradiated from antenna element 121f are reflected at reflection area 132f.
• Reflection area 132g corresponds to antenna element 121g, and radio waves emitted from antenna element 121g are reflected in reflection area 132g.
• Each of the reflection areas 132a, 132b, 132c, 132d, 132e, 132f, and 132g is an area where radio waves of sufficient strength for object detection are reflected.
• Each of the reflection areas 132a, 132b, 132c, 132d, 132e, 132f, and 132g may be defined as an area that includes at least an area where the strength of the radio waves irradiated from each of the antenna elements 121a, 121b, 121c, 121d, 121e, 121f, and 121g is -3 dB or more relative to the radio wave strength of the peak of the main lobe.
• Adjacent reflective areas partially overlap with each other.
• a portion of reflective area 132a overlaps with a portion of reflective area 132b.
• a portion of reflective area 132b overlaps with a portion of reflective area 132c.
• a portion of reflective area 132c overlaps with a portion of reflective area 132d.
• a portion of reflective area 132d overlaps with a portion of reflective area 132e.
• a portion of reflective area 132e overlaps with a portion of reflective area 132f.
• a portion of reflective area 132f overlaps with a portion of reflective area 132g.
• the reflective surface 131 may include all of the reflective areas 132a, 132b, 132c, 132d, 132e, 132f, and 132g. In this case, the left end of the leftmost reflective area 132a and the right end of the rightmost reflective area 132g are included in the range of the reflective surface 131.
• antenna element 121a will be described as a representative, but the same applies to antenna elements 121b, 121c, 121d, 121e, 121f, and 121g.
• Antenna element 121a is an array antenna including three elements 122a, 122b, and 122c aligned in the second direction Y.
• the length X4 of antenna element 121a in the first direction X (hereinafter also referred to as "element width") is determined by the length in the first direction of central element 122b among elements 122a, 122b, and 122c.
• Element 122b is the element with the longest length in the first direction X among elements 122a, 122b, and 122c.
• the length of the reflective surface 131 in the first direction X can be determined based on the element width X4.
• the length (hereinafter also referred to as "area width") X3 (see FIG. 18) of each of the reflective areas 132a, 132b, 132c, 132d, 132e, 132f, and 132g in the first direction X can be determined based on the element width X4, and the length of the reflective surface 131 in the first direction X can be determined so that all of the reflective areas 132a, 132b, 132c, 132d, 132e, 132f, and 132g are included in the reflective surface 131.
• Line 123a is a line obtained by projecting the center line of the leftmost antenna element 121a in the first direction X onto the reflecting surface 131 along a direction perpendicular to the first direction X.
• Line 123g is a line obtained by projecting the center line of the rightmost antenna element 121g in the first direction X onto the reflecting surface 131 along a direction perpendicular to the first direction X.
• the reflecting surface 131 includes an area between line 124a, which is half the area width X3 to the left of line 123a, and line 124g, which is half the area width X3 to the right of line 123g, in the first direction X.
• the length X1 of the reflecting surface 131 in the first direction X is equal to or greater than the length between line 124a and line 124g, i.e., the length X5 in the first direction X between the left end of the leftmost reflecting area 132a and the right end of the rightmost reflecting area 132g.
• the reflector 130 may be a reflectarray reflector. By appropriately setting the reflection angle of the radio waves of the reflectarray reflector, it is possible to adjust the irradiation area 40B (see FIG. 4B ) of the radio waves reflected by the reflector 130, regardless of the angle ( ⁇ 3 in FIG. 12 ) between the reflector and the antenna surface 120a.
• the reflector 130 is housed in the housing 150, but this is not limiting. See FIG. 25.
• the reflector 130B is disposed outside the housing 150B of the radio wave sensor 100B. Specifically, the reflector 130B is attached above the transmitting/receiving surface 151B of the housing 150B. The lower surface of the reflector 130B is the reflecting surface 131B. Even with this configuration, a portion of the radio waves irradiated upward from the transmitting/receiving surface 151B can be reflected downward by the reflecting surface 131B of the reflector 130B, and the detection area can be expanded.
• the reflector 130 is a flat plate, but is not limited to this. See FIG. 26.
• the reflector 130C is configured as a bent plate. That is, the reflector 130C includes a first portion 133a and a second portion 133b. One end of the first portion 133a is fixed to the housing 150. The first portion 133a and the second portion 133b are each flat, and a certain angle other than 0° is provided between the first portion 133a and the second portion 133b.
• a reflective surface is provided on at least one of the first portion 133a and the second portion 133b.
• a reflective surface may be provided on the bottom surface of both the first portion 133a and the second portion 133b, or a reflective surface may be provided only on the bottom surface of the first portion 133a, or a reflective surface may be provided only on the bottom surface of the second portion 133b.
• the reflector 130D is configured as a plate curved in an arc shape.
• the curvature of the reflector 130D may be constant, or the curvature may change midway.
• a reflective surface is provided on at least a portion of the underside of the reflector 130D. That is, the reflective surface may be provided on the entire underside of the reflector 130D, or only on the front portion of the underside of the reflector 130D, or only on the rear portion of the reflector 130D.
• the reflector 130E is not rectangular, but has a shape based on the intensity distribution of radio waves reflected by the reflector 130E.
• the front end of the reflector 130E has a shape in which multiple parabolic protrusions are arranged in the X direction. Each protrusion has the same shape as the outer edge of the reflection areas 132a, 132b, 132c, 132d, 132e, 132f, and 132g shown in FIG. 18.
• the front end of the reflector 130E has a shape that connects the outer edges of the reflection areas 132a, 132b, 132c, 132d, 132e, 132f, and 132g. This allows the reflector 130E to reflect radio waves of sufficient strength for object detection, and allows the reflector 130E to be configured small.

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  • 2024-02-08 CN CN202480023655.2A patent/CN120981733A/zh active Pending
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  • 2024-02-08 WO PCT/JP2024/004228 patent/WO2024209785A1/ja not_active Ceased

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