Radio wave sensor

Abstract

Provided is a radio wave sensor capable of reflecting upward radio waves toward the ground and diffusing or converging the reflected waves in the left-right direction. The radio wave sensor comprises: a radiation antenna that is attached at a prescribed height from the ground and has an antenna surface perpendicular to the ground or an antenna surface inclined obliquely toward the ground; a reception antenna that receives reflected waves of radio waves radiated by the radiation antenna; a detection unit that analyzes the reflected waves received by the reception antenna and detects an object; and a reflection member that is provided above the radiation antenna and has a reflection surface for reflecting upward radio waves from the radiation antenna toward the ground. When viewed from the front of the antenna surface, the reflection surface is configured to have a convex shape or a concave shape with respect to the ground.

Description

Radio wave sensor

[0001] The present invention relates to a radio wave sensor that detects an object by using the reflection of radio waves and, for example, detects an intruder.

[0002] Patent Document 1 describes a radio wave sensor having an antenna that transmits and receives radio waves and a reflector disposed above the antenna. In this sensor, radio waves are reflected by the reflector so as to be directed toward the ground, increasing the radio wave intensity below the sensor and forming a detection area (hereinafter referred to as a foot detection area) below the sensor.

[0003] The reflector of this sensor is provided such that the left-right direction component is horizontal when viewed from the front of the antenna.

[0004] International Publication No. 2024 / 047998

[0005] However, in the above sensor, since the left-right direction component of the reflector viewed from the front is horizontal, the reflected waves cannot be diffused in the left-right direction, and the width of the foot detection area in the left-right direction cannot be increased. In this case, an object that crosses the foot detection area at high speed has a short residence time in the area, making it difficult to accurately detect it.

[0006] Also, if the reflector is horizontal in the left-right direction as in the above sensor, the reflected waves cannot be converged, and there is a possibility that the object detection sensitivity below the sensor cannot be ensured.

[0007] Therefore, the present invention has been made to solve the above-described problems, and an object of the present invention is to provide a radio wave sensor that can reflect radio waves directed upward toward the ground and can diffuse or converge the reflected waves in the left-right direction.

[0008] In other words, the present invention has the following configuration: [1] A radio wave sensor comprising: a radiating antenna mounted at a predetermined height from the ground and having an antenna surface perpendicular to the ground or an antenna surface inclined diagonally toward the ground; a receiving antenna that receives reflected waves of radio waves radiated by the radiating antenna; a detection unit that analyzes the reflected waves received by the receiving antenna and detects an object; and a reflective member provided above the radiating antenna and having a reflective surface that reflects radio waves directed upward from the radiating antenna toward the ground, wherein, when viewed from the front of the antenna surface (hereinafter referred to as the front), the reflective surface is convex or concave with respect to the ground. (Effects) With this configuration, the following effects can be achieved. In other words, the reflective surface, which is convex or concave with respect to the ground, can reflect radio waves while diffusing them in the left-right direction or while converging them. As a result, a foot detection area with a wider left-right width than conventional models can be formed below the radio wave sensor, or a foot detection area with better sensitivity than conventional models can be formed.

[0009] [2] The radio wave sensor according to [1], wherein, when viewed from the front, the width of the spread in the left-right direction when the radio waves reflected by the reflective surface reach the ground is greater than the width of the spread in the left-right direction when it is assumed that the radio waves propagated the same distance without passing through the reflective surface. (Effect) With this configuration, a wide foot detection area is formed below the radio wave sensor, so even objects that cross the foot detection area at high speed can be detected accurately because their dwell time in the area is longer.

[0010] [3] The radio wave sensor according to [1] or [2], wherein, when viewed from the front, the reflective surface has a first inclined plane whose right end is inclined downward and a second inclined plane whose left end is inclined downward. (Effect) With this configuration, the convex or concave shape of the reflective surface is formed by two inclined planes that are inclined in opposite directions. This makes the geometrical optical design of the reflective surface for forming the foot detection area easier than when the reflective surface is formed as a curved surface.

[0011] [4] The radio wave sensor according to [3], wherein, when viewed from the front, the reflective surface further has a central plane whose left-right component is horizontal, the first inclined plane extends from one end of the central plane in the left-right direction, and the second inclined plane extends from the other end. (Effects) For example, if the reflective surface when viewed from the front forms a V shape, that is, if a second inclined plane that rises to the right is provided immediately to the right of a first inclined plane that slopes downward to the right, these two surfaces are connected at a steep angle, and an area with extremely low radio wave intensity may be created below the boundary. Also, if the reflective surface when viewed from the front forms an inverted V shape, that is, if a first inclined plane that slopes downward to the right is provided immediately to the right of a second inclined plane that slopes upward to the right, these two surfaces are connected at a steep angle, and an area with extremely high radio wave intensity may be created below the boundary. In this way, if inclined surfaces that tilt in opposite directions are lined up in a row on the reflective surface, a gap in detection sensitivity is likely to occur within the foot detection area. In contrast, with configuration [4], the first and second inclined planes are connected to the horizontal central plane at relatively gentle angles, which suppresses the formation of areas with extremely high or low radio wave intensity within the foot detection area and helps to equalize the detection sensitivity.

[0012] [5] The radio wave sensor according to [1] or [2], wherein the reflective surface is arc-shaped when viewed from the front. (Effect) With this configuration, it is easy to form a foot detection area with uniform sensitivity below the radio wave sensor.

[0013] [6] The radio wave sensor according to any one of [1] to [5], wherein the reflective surface reflects radio waves from the radiating antenna such that some or all of the radio waves that are directed diagonally upward and have an intensity lower than a predetermined value overlap with the radio waves that are directed diagonally downward and have an intensity lower than a predetermined value, without passing through the reflective surface. (Effect) With this configuration, low-intensity radio waves that cannot be used for detection can be superimposed to form a foot detection area below the sensor, improving the efficiency of radio wave utilization.

[0014] [7] A radio wave sensor according to any one of [1] to [6], further comprising a housing for housing the reflective member, wherein the housing has a visor that covers the front side of the antenna surface from above, and the visor is made of a material that transmits radio waves. (Effect) With this configuration, the reflective member is housed and protected in the visor, and the appearance of the visor of the radio wave sensor can be made different from the shape of the reflective member housed inside it.

[0015] According to the present invention configured in this manner, it is possible to provide a radio wave sensor that can reflect upward-directed radio waves toward the ground, and also diffuse or converge the reflected waves in the left-right direction.

[0016] A schematic diagram of a radio wave sensor according to the first embodiment of the present invention. A transmission perspective view of the radio wave sensor according to the same embodiment. A schematic diagram showing the antenna substrate in the same embodiment. A schematic diagram showing the reflective member in the same embodiment. A schematic diagram of the detection area viewed from the left in the same embodiment. A schematic diagram of the detection area viewed from above in the same embodiment. A schematic diagram of a radio wave sensor according to the second embodiment of the present invention. A transmission perspective view of the radio wave sensor according to the same embodiment. A schematic diagram showing the reflective member in the same embodiment. A schematic diagram showing the reflective member in another embodiment. A schematic diagram showing the reflective member in another embodiment.

[0017] Hereinafter, a first embodiment of the radio wave sensor of the present invention will be described with reference to the drawings.

[0018] <First Embodiment> 1. Overview The radio wave sensor of this embodiment is used as a security device to detect and alert when a suspicious person enters a predetermined detection area. The radio wave sensor 100 is a MIMO (Multi-In-Multi-Out) radar sensor that uses millimeter waves, for example. Millimeter waves are electromagnetic waves with a frequency of 30 GHz to 300 GHz.

[0019] 2. Device Configuration Specifically, as shown in Figures 1 and 2, the radio wave sensor 100 comprises a radiating antenna 2 mounted at a predetermined height from the ground, a receiving antenna 3 that receives reflected waves of radio waves radiated by the radiating antenna 2, a detection unit 4 that analyzes the reflected waves received by the receiving antenna 3 to detect intruders, and a reflective member 5 provided above the radiating antenna 2. The ground may be a floor surface or a surface parallel to the ground or floor surface.

[0020] The radiating antenna 2, receiving antenna 3, detection unit 4, and reflecting member 5 are housed in a common enclosure H and mounted at a predetermined height from the ground. The predetermined height is, for example, 1.0 m to 3.0 m. As shown in Figure 1, the enclosure H is a vertically elongated columnar shape and is mounted on a wall, column, ceiling, etc.

[0021] As shown in Figures 1 and 2, the housing H has a main body H1 that houses the radiating antenna 2, the receiving antenna 3, and the detection unit 4, and a canopy H2 that houses the reflective member 5 and is provided above the main body H1. The housing H is made of, for example, resin. The canopy H2 protrudes forward from the main body H1 and covers the front side of the main body H1 from above.

[0022] As shown in Figure 3, the radiating antenna 2 is a planar antenna such as a so-called microstrip antenna, and consists of a radiating element 21 that radiates radio waves (in this case, millimeter waves), an antenna substrate B on which the radiating element 21 is provided on the front surface, a ground conductor plate (not shown) provided on the back surface of the antenna substrate B, and a signal supply circuit (not shown) provided on the antenna substrate B that supplies high-frequency signals to the radiating element 21.

[0023] The radiating elements 21 are, for example, metal patterns formed by photolithography on the antenna substrate B. Here, the radiating elements 21 are rectangular in shape, and four of them are provided on the antenna substrate B. As described above, the radio wave sensor 100 is a MIMO type radar sensor, and radio waves are emitted sequentially and independently from the four radiating elements 21.

[0024] Antenna substrate B is a so-called dielectric substrate made of a resin with low dielectric loss, such as PTFE (polytetrafluoroethylene). As shown in Figure 2, antenna substrate B is flat and is held inside the housing H with its front surface perpendicular to the ground.

[0025] As mentioned above, the front surface of antenna substrate B is the surface on which the radiating element 21 is provided, and this surface will be referred to as the antenna surface AS. In other words, the antenna surface AS is the radiating side of the planar radiating antenna 2.

[0026] Hereinafter, the direction perpendicular to the vertical direction on this antenna surface AS will be referred to as the left-right direction, and the direction perpendicular to both the left-right and vertical directions will be referred to as the front-back direction. The front-back direction here is perpendicular to the antenna surface AS. In this embodiment, viewing the antenna surface AS from the front will be referred to as viewing it from the front. Furthermore, in the front-back direction, the front side of the antenna substrate B, i.e., the antenna surface AS side, will be considered the front, and the back side will be considered the rear, while the left and right directions in the left-right direction will be determined by viewing from the front.

[0027] A radome 6 is provided in front of the antenna surface AS, which protects the antenna surface AS and allows radio waves from the radiating antenna 2 to pass through. In addition, a heat dissipation fin 7 is provided on the back side of the antenna substrate B to dissipate heat from the antenna substrate B to the outside of the housing H.

[0028] As shown in Figure 3, the receiving antenna 3 is a planar antenna such as a so-called microstrip antenna, and consists of an antenna substrate B formed as a dielectric substrate, four receiving elements 31 provided on one side of the antenna substrate B to receive reflected millimeter waves radiated by the radiating element 21, a ground conductor plate (not shown) printed on the other side, and a signal processing circuit (not shown) that performs processing such as amplifying the reflected wave signals output from the receiving elements 31 based on the received reflected waves.

[0029] The receiving element 31 is, for example, a metal pattern formed on the antenna substrate B by a process such as photolithography. Here, the receiving element 31 is rectangular in shape, and four of them are arranged in a row on the antenna substrate B. As described above, the radio wave sensor 100 is a MIMO type radar sensor, and the four receiving elements 31 each independently receive the reflected waves of the radio waves emitted by each radiating element 21.

[0030] The antenna substrate B of the receiving antenna 3 in this embodiment is the same as that of the radiating antenna 2. Therefore, the radiating element 21 and the receiving element 31 are provided on the same antenna surface AS.

[0031] The radiating antenna 2 and the receiving antenna 3 may be mounted on separate antenna substrates. Furthermore, the number or arrangement of the radiating elements 21 and receiving elements 31 mounted on the antenna substrate B is not limited to the above; one or more elements are sufficient.

[0032] The detection unit 4 is physically a computer equipped with a CPU, memory, I / O interface, communication interface, etc., and in this case, it is a microcontroller mounted on the antenna board B. The detection unit 4 performs its functions through the cooperation of the CPU and its peripheral devices according to the program stored in the memory.

[0033] As shown in Figure 3, the detection unit 4 analyzes the reflected waves received by the receiving antenna 3 to detect intruders. For example, the detection unit 4 receives a reflected wave signal from the receiving antenna 3 indicating the intensity of the reflected waves received by the receiving antenna 3, compares the intensity of the reflected waves with a predetermined detection threshold, and detects the presence or absence of an intruder. The detection unit 4 then outputs the detection result as a detection result signal. The detection result signal is a signal for issuing an alarm to indicate the presence of an intruder, and is transmitted to, for example, a security control device connected to an alarm or camera, a monitoring server managed by a security company, or a mobile terminal of the person who installed the radio wave sensor 100. The security control device, monitoring server, etc., that receive the detection result signal indicating the presence of an intruder then issues an alarm, notifies an operator, or otherwise makes an alert.

[0034] Furthermore, the detection unit 4 of this embodiment also detects the distance or position of the detected intruder. For example, the detection unit 4 calculates the distance based on the time difference between the radiated wave from the radiating antenna 2 and the reflected wave received by the receiving antenna 3, and detects the intruder's position from this distance and the angle of the reflected wave calculated based on the phase difference of the reflected waves received by the multiple receiving elements 31.

[0035] As shown in Figures 2 and 4, the reflective member 5 is provided above the antenna substrate B and has a reflective surface 50 that reflects radio waves directed upward from the radiating antenna 2 toward the ground. The reflective member 5 is held within the housing H on the antenna surface AS side of the antenna substrate B and above the antenna substrate B, in a position where the reflective surface 50 faces toward the ground. Specifically, the reflective member 5 is in the shape of a plate with the reflective surface 50 formed on one of its surfaces.

[0036] The reflective surface 50 is made of a material that reflects radio waves, and is, for example, a metal film formed by plating or the like. If the reflective member 5 is a metal plate, the reflective surface 50 may be its surface or the like. In this embodiment, the reflective surface 50 is convex relative to the ground when viewed from the front.

[0037] As shown in Figure 4, the reflective surface 50 is formed as a polyhedron having three planes, and its three planes form a convex shape. Specifically, the reflective surface 50 has a central plane 51 whose left-right component is horizontal when viewed from the front, a first inclined plane 52 extending from the left end 51a of the central plane 51, and a second inclined plane 53 extending from the right end 51b of the central plane 51. The right end 52b of the first inclined plane 52 is inclined downward at a predetermined angle, and the left end 53a of the second inclined plane 53 is inclined downward at a predetermined angle, so that the central plane 51 protrudes from the ground. Here, the first inclined plane 52 and the second inclined plane 53 are arranged to be mirror-symmetrical when viewed from the front.

[0038] Furthermore, when viewed from the left or right, the front end of the reflective surface 50 is inclined toward the ground at a predetermined angle. In addition, the outer shape of the canopy portion H2 that houses the reflective surface 50 is also formed to tilt forward in accordance with the reflective surface 50.

[0039] 3. Detection Area For the radio wave sensor 100 having the reflection member 5 provided above the antenna surface AS as described above, the set detection area will be described in detail while referring to FIGS. 5 and 6.

[0040] Note that the detection area is an area where, when a reflected wave from within that area is received by the receiving antenna 3, the intensity of the reflected wave exceeds a predetermined detection threshold of the detection unit 4.

[0041] FIG. 5(i) shows the detection area formed when the radio wave from the radiating antenna propagates without being reflected by a reflecting surface or the like, viewed from the left side. The detection area forms a vertically symmetric sector with respect to the horizontal line passing through the center of the antenna surface and perpendicular to the antenna surface. Further, around the detection area, although radio waves are radiated from the radiating antenna 2, a low-sensitivity area is formed where, when a reflected wave from within that area is received by the receiving antenna 3, the intensity of the reflected wave is below a predetermined detection threshold.

[0042] FIG. 5(ii) shows the detection area of the radio wave sensor 100 according to the present embodiment, viewed from the left side. Similar to the case where the reflection member is not provided, a fan-shaped main detection area X is formed in front of the antenna surface AS. Further, due to the reflecting surface 50, the radio wave radiated above the main detection area X is reflected downward, so that a foot detection area Y where the intensity of the reflected wave exceeds a predetermined detection threshold is formed diagonally below the radio wave sensor 100.

[0043] The foot detection area Y is an area where the radio wave having downward directivity by the reflecting surface 50 and the radio wave propagating directly downward from the radiating antenna 2 overlap.

[0044] In this embodiment, the radio wave reflected by the reflecting surface 50 is a radio wave having an intensity lower than a predetermined value among the radio waves radiated from the radiating antenna 2, specifically, a radio wave having an intensity such that the intensity of the generated reflected wave is below a predetermined detection threshold.

[0045] FIG. 6(i) is a top view of the detection area of a radio wave sensor including a flat reflecting member having a single horizontal reflecting surface when viewed from the front. The spread angle of the underfoot detection area is almost the same as that of the main detection area.

[0046] FIG. 6(ii) is a top view of the detection area of the radio wave sensor 100 according to the present embodiment. In the present embodiment, radio waves are reflected by the convex reflecting surface 50 so as to spread in the left - right direction. Specifically, by the central plane 51, the first inclined plane 52, and the second inclined plane 53, radio waves are reflected so as to spread in three directions (downward, lower left, lower right). In FIG. 6(ii), for the sake of expressing the radio waves as traveling straight, the underfoot detection area Y is shown as if it is completely divided into three parts. However, in reality, as the radio waves (millimeter waves) spread and propagate, an underfoot detection area Y is formed which is connected although part of it has low sensitivity.

[0047] The spread angle of the underfoot detection area Y when viewed from above is larger than that of the main detection area X. The left - right width of the underfoot detection area Y on the ground is larger than the left - right width of the reflecting surface 50.

[0048] Also, the left - right width of the underfoot detection area Y formed by the reflecting surface 50 of the present embodiment on the ground is larger than the left - right width of the underfoot detection area formed by a reflecting surface of a single horizontal plane when viewed from the front as shown in FIG. 6(i).

[0049] Furthermore, in this embodiment, the lateral spread width of the radio waves reflected by the reflective surface 50 when they reach the ground is set to be 20% or more wider than the spread width when they propagate the same distance without passing through the reflective surface 50. In other words, the angle of spread of the radio waves reflected by the reflective surface 50 as viewed from the front is set to be larger than the angle of spread of the radio waves incident on the reflective surface 50 as viewed from the front. In addition, in order to ensure the detection sensitivity of the foot detection area Y, it is desirable that the increase rate be 40% or less. Note that the increase rate of the spread width is not limited to the above. It is desirable that it spreads by at least 10%, but a smaller increase rate is also acceptable. It may also spread by 40% or more. Furthermore, it is desirable that the lateral width of the foot detection area Y on the ground be increased by a width equivalent to the thickness of the human body, for example, 15 cm or more.

[0050] 4. Effects of the First Embodiment Since a wide foot detection area Y is formed in the left-right direction, the time that an intruder crossing below the radio wave sensor 100 in the left-right direction remains within the foot detection area Y increases. As a result, the radio wave sensor 100 has more opportunities to identify intruders, making detection easier. In addition, because the left-right width of the foot detection area Y is wide, it is easier to obtain time-series information on intruders as they cross it, and it is also easier to detect their direction of movement.

[0051] Since the concave shape of the reflective surface 50 is formed by three planes 51, 52, and 53, geometric optics design is easy. Furthermore, since the two inclined planes 52 and 53 are connected via the central plane 51, the gap in detection sensitivity within the foot detection area can be reduced.

[0052] [Second Embodiment] As shown in Figures 7 and 8, the radio wave sensor 100 of the second embodiment has a reflective surface 50 formed as a curved surface. Note that the configuration common to the radio wave sensor 100 of the first embodiment will not be described.

[0053] As shown in Figures 8 and 9, the reflective member 5 of the second embodiment is a curved mirror having a reflective surface 50 that forms an arc shape when viewed from the front, and is concave with respect to the ground. The reflective surface 50 may be a non-arc curved surface, or it may be a sphere or the like.

[0054] Furthermore, although the reflective surface 50 in this embodiment is provided on the lower surface of the eaves portion H2 so as to be exposed outside the housing H, it is not limited to this and may be housed within the eaves portion H2.

[0055] In this embodiment, the reflective surface 50, when viewed from the front, is concave relative to the ground. As a result, the radio waves reflected by this reflective surface 50 propagate by converging once in the left-right direction before spreading out. In order to form a wide foot detection area Y in the left-right direction, the curvature of the reflective surface 50 and the possible mounting positions of the reflective surface 50 are set such that the point where the radio waves converge due to the reflective surface 50 is above half the height from the ground to the reflective surface 50.

[0056] Furthermore, in this embodiment, since the reflective surface 50 is a curved surface, the foot detection area Y, when viewed from above, is formed as a continuous area in the left-right direction.

[0057] [Effects of the second embodiment] Since the reflective surface 50 is arc-shaped when viewed from the front, the radio wave intensity in the foot detection area Y is made uniform in the left-right direction.

[0058] Since the reflective surface 50, when viewed from the front, is concave relative to the ground, it can reflect more radio waves radiated diagonally upwards to the right or diagonally upwards to the left from the antenna surface AS downwards than if it were convex, resulting in better radio wave efficiency.

[0059] [Other Embodiments] The present invention is not limited to the embodiments described above. For example, the radio wave sensor may be incorporated into various systems not only as a security device, but also as a human detection sensor that detects people within a predetermined detection area. It may also be used as a sensor to detect objects.

[0060] The radio wave sensor may not only utilize millimeter waves, but also microwaves (electromagnetic waves with frequencies between 3 GHz and 30 GHz), or any other type of electromagnetic wave (electromagnetic waves with frequencies of 3 THz or less).

[0061] Furthermore, the radio wave sensor is not limited to those that measure angles using the MIMO method. Angular measurement may also be performed using phased array methods, mechanical operation methods, etc. Regarding the distance measurement method, various existing methods such as pulse method, FMCW method, and Doppler method can be adopted.

[0062] In the embodiments described above, the antenna surface was configured to be perpendicular to the ground, but the antenna surface may be tilted at a predetermined angle in the elevation direction from the perpendicular position to the ground. For example, tilting the antenna surface forward toward the ground makes it easier to detect the area directly beneath the radio wave sensor. This is particularly noticeable when the sensor is installed at a high altitude.

[0063] The reflective member 5 and the reflective surface 50 may be as shown in Figure 10. This reflective surface 50 is formed as a polyhedron having four planes, and has a first inclined plane 52 and a second inclined plane 53 that form a convex shape with respect to the ground near the center when viewed from the front, a left end plane 54 extending from the left end of the first inclined plane 52, and a right end plane 55 extending from the right end of the second inclined plane 53. With such a reflective surface 50, a foot detection area can be formed with two highly sensitive areas on the left and right. In this case, highly sensitive areas can be provided on both the left and right sides that constitute the outer edge of the area to be monitored, making it easier to detect intrusion into the area.

[0064] Furthermore, the reflective member 5 and the reflective surface 50 may be as shown in Figure 11. This reflective surface 50 has two curved surfaces 56 and 57 that form different concave shapes when viewed from the front. With such a reflective surface 50, it is possible to form a foot detection area with two highly sensitive regions on the left and right sides.

[0065] The reflective surface may be positioned horizontally in the front-to-back direction, or its rear end may be inclined at a predetermined angle toward the ground. Furthermore, if the reflective surface is composed of multiple planes, there may be gaps between each of these planes.

[0066] Furthermore, the reflective element is not limited to a plate shape; it can be any shape as long as it has a reflective surface facing the ground. The reflective surface can also take various forms, such as a combination of a flat and a curved surface, or an asymmetrical surface. The reflective surface only needs to be convex or concave relative to the ground when viewed from the front.

[0067] The point where radio waves converge due to a concave reflective surface relative to the ground may be below half the height from the ground to the reflective surface. This allows for the formation of a foot-level detection area with high detection sensitivity.

[0068] The reflective surface may be designed to reflect radio waves emitted from the radiating antenna, specifically those that are directed diagonally upward and have an intensity higher than a predetermined value, toward the ground.

[0069] The shape of the visor does not have to correspond to the shape of the reflective member. Furthermore, the visor does not have to be provided, and the reflective member and reflective surface may be held within the housing while exposed to the outside of the housing.

[0070] The detection unit may, upon detecting an intruder within the detection area, further determine whether the intruder has entered a predetermined security area set within that area. It may then issue an alarm based on this determination. In a foot-level detection area that extends horizontally when viewed from above, if the central part is set as the security area, an alarm can be triggered only when an intruder is detected near the area directly below the radio wave sensor. It is preferable that the security area in the main detection area and the security area in the foot-level detection area be set separately.

[0071] The detection unit should detect the direction of movement of an object detected in the foot-level detection area, and should also output the detected direction of movement.

[0072] Furthermore, it goes without saying that the present invention is not limited to the embodiments described above, and various modifications are possible without departing from its spirit.

[0073] According to the present invention, it is possible to provide a radio wave sensor that can reflect upward-directed radio waves toward the ground, and also diffuse or converge the reflected waves in the left-right direction.

[0074] 100: Radio wave sensor 2: Radiating antenna 3: Receiving antenna 4: Detection unit 5: Reflective member 50: Reflective surface 51: Central plane 52: First inclined plane 53: Second inclined plane AS: Antenna surface H: Housing H2: Overhang

Claims

1. A radio wave sensor comprising: a radiating antenna mounted at a predetermined height above the ground and having an antenna surface perpendicular to the ground or an antenna surface inclined diagonally toward the ground; a receiving antenna that receives reflected waves of radio waves radiated by the radiating antenna; a detection unit that analyzes the reflected waves received by the receiving antenna and detects an object; and a reflective member provided above the radiating antenna and having a reflective surface that reflects radio waves directed upward from the radiating antenna toward the ground, wherein, when viewed from the front of the antenna surface, the reflective surface is convex or concave relative to the ground.

2. The radio wave sensor according to claim 1, wherein, when viewed from the front, the width of the spread in the left-right direction when the radio waves reflected by the reflective surface reach the ground is greater than the width of the spread in the left-right direction when it is assumed that the radio waves propagated the same distance without passing through the reflective surface.

3. The radio wave sensor according to claim 1, wherein, when viewed from the front, the reflective surface has a first inclined plane whose right end is inclined downward and a second inclined plane whose left end is inclined downward.

4. The radio wave sensor according to claim 3, wherein, when viewed from the front, the reflective surface further has a central plane whose left-right component is horizontal, the first inclined plane extends from one end of the central plane in the left-right direction, and the second inclined plane extends from the other end.

5. The radio wave sensor according to claim 1, wherein, when viewed from the front, the reflective surface is arc-shaped.

6. The radio wave sensor according to claim 1, wherein the reflective surface reflects radio waves emitted from the radiating antenna such that some or all of the radio waves that are directed diagonally upward and have an intensity lower than a predetermined value overlap with the radio waves that are directed diagonally downward and have an intensity lower than a predetermined value, without passing through the reflective surface.

7. The radio wave sensor according to claim 1, further comprising a housing for housing a reflective member, wherein the housing has a visor portion that covers the front side of the antenna surface from above, and the visor portion is made of a material that transmits radio waves.

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