radar equipment

Abstract

Realization of a radar system equipped with a radome capable of suppressing the reception of reflected waves from objects outside the detection range. [Solution] The radar device 1, which detects the presence or absence of an object within a detection range by transmitting and receiving radio waves, comprises an antenna unit 10 and a radome 20. The antenna unit 10 has a transmitting unit 14 and a receiving unit 16 located at separate positions in the direction normal to the front direction of the antenna. The radome 20 has a convex shape in the direction of the front direction of the antenna. The radome 20 has a radio wave-transmitting part 22 provided at the top and a radio wave-absorbing part 24 provided in the peripheral part of the top that absorbs radio waves. The transmitting unit 14 is located behind the top or behind the transmissive part 22 in a front view which is the opposite direction of the front direction of the antenna.

Description

Technical Field

[0001] The present invention relates to a radar device.

Background Art

[0002] In an obstacle detection device using a radar device, as a technique for detecting only obstacles within the detection range and not detecting objects outside the detection range as obstacles, a technique based on the difference between the received signal in the radar device and a reference signal corresponding to background noise when there are no obstacles within the detection range (search range) is well known (see, for example, Patent Document 1).

[0003] Also, as a technique of a conventional radar device provided with a radome, a technique is known in which radar waves are radiated in all directions through the radome, or reflected waves from an object hit by radar waves are received from all directions through the radome (see, for example, Patent Document 2).

Prior Art Documents

Patent Documents

[0004]

Patent Document 1

Patent Document 2

Summary of the Invention

Problems to be Solved by the Invention

[0005] By the way, in an environment where many objects exist, a radar device is likely to be affected by multipath. Among the received radio waves (received waves), in addition to the direct reflected waves obtained by the transmitted radio waves (transmitted waves) hitting an object and reflecting, there are also included indirect reflected waves obtained by hitting another object and reflecting, making it difficult to detect the position and angle of the object with respect to the radar device. This is the influence of multipath.

[0006] Therefore, in order to detect an obstacle with high accuracy when it is present within a certain detection range (search range), it is necessary to minimize the amount of reflected waves (including both direct and indirect reflected waves) received by the radar device from objects outside the detection range.

[0007] The problem that this invention aims to solve is to realize a radar device equipped with a radome that can suppress the reception of reflected waves from objects outside the detection range. [Means for solving the problem]

[0008] The first invention for solving the above problem is: A radar device that detects the presence or absence of an object within its detection range by transmitting and receiving radio waves, An antenna unit having a transmitting unit and a receiving unit located at separate positions in the direction normal to the front direction of the antenna, The radome having a convex shape in the direction of the front of the antenna, Equipped with, The aforementioned radome is A transparent section that transmits radio waves is provided at the top, An absorbing section for absorbing radio waves is provided in the peripheral portion of the aforementioned top portion, It has, The transmitting unit is located behind the top portion or behind the transparent portion when viewed from the front, which is in the opposite direction to the front of the antenna. It is a radar device.

[0009] According to the first invention, it is possible to realize a radar device equipped with a radome that can suppress the reception of reflected waves from objects outside the detection range. The transmitting and receiving parts of the antenna are located apart in the direction normal to the front direction of the antenna, and in a front view which is opposite to the front direction of the antenna, the transmitting part is located behind the top of the radome or behind the transparent part. Therefore, by installing the radar device so that the direction of the displacement of the receiving part relative to the transmitting part corresponds to the direction of the detection range which is biased relative to the front direction of the antenna, the direction of transmission and reception of radio waves is generally restricted to the direction of the detection range. This makes it possible to suppress reflected waves from objects outside the detection range that are received by the radar device.

[0010] The second invention is, in the above invention, The detection range is included in a planar recommended detection angle range defined by the direction of one end and the direction of the other end, with the direction along the front of the antenna being one end direction. The antenna section is positioned such that, in a side view perpendicular to the front direction and the normal direction of the antenna, the side of the receiving section's installation position relative to the transmitting section and the side of the other end relative to the one end are opposite, with the transmitting section and the receiving section separated from each other. It is a radar device.

[0011] According to the second invention, it becomes possible for the receiving unit to appropriately receive reflected waves from a detection range that is biased in direction relative to the front direction of the antenna.

[0012] The third invention is, in the above invention, The receiving unit is located behind the transparent section in the front view. It is a radar device.

[0013] According to the third invention, the receiving unit can appropriately receive reflected waves from the detection range in the direction in front of the antenna and in directions biased with respect to the direction in front of the antenna.

[0014] The fourth invention is, in the above invention, The inner surface of the absorption part is an arc-shaped curved surface centered on the installation position of the transmission part. It is a radar device.

[0015] According to the fourth invention, since the inner surface of the absorption part is an arc-shaped curved surface centered on the installation position of the transmission part, the radio wave transmitted from the transmission part toward the absorption part will be incident perpendicularly to the absorption part, and it becomes possible to efficiently suppress the radiation of radio waves outside the antenna in the direction from the transmission part toward the absorption part.

[0016] The fifth invention is in the above-mentioned invention. The inner surface of the absorption part is an arc-shaped curved surface centered on the installation position of the transmission part, The diameter of the curved surface is such that the first diameter on the side of the installation position of the receiving part with reference to the transmission part is larger than the second diameter on the side opposite to the side of the installation position of the receiving part with reference to the transmission part. It is a radar device.

[0017] According to the fifth invention, since the inner surface of the absorption part is an arc-shaped curved surface centered on the installation position of the transmission part, the radio wave transmitted from the transmission part toward the absorption part will be incident perpendicularly to the absorption part, and it becomes possible to efficiently suppress the radiation of radio waves outside the antenna in the direction from the transmission part toward the absorption part. Also, since the diameter of the arc-shaped curved surface is such that the first diameter on the side of the installation position of the receiving part with reference to the transmission part is larger than the second diameter on the side opposite to the side of the installation position of the receiving part with reference to the transmission part, it becomes possible to appropriately receive the reflected wave from the front direction of the antenna at the receiving part.

[0018] The sixth invention is in the above-mentioned invention. The transmission part and the absorption part have a thickness that is an integer multiple of the half wavelength of the radio wave, The absorption part contains a reflecting member that reflects the radio wave, and the distance from the inner surface is such that the phase of the reflected wave is 180 degrees different from that of the incident wave to the reflecting member. It is a radar device.

[0019] According to the sixth invention, a radome can be made that minimizes the loss of radio waves transmitted from the transmitting unit as they pass through the penetrating unit, thereby improving the detection accuracy of the radar device. Furthermore, since the incident wave, which is a radio wave transmitted from the transmitting unit and incident on the absorbing unit, is absorbed by the incident wave canceling out with the reflected wave reflected by the reflective member of the absorbing unit, it is possible to make a radome that prevents the reflected wave of the incident wave from being received by the receiving unit.

[0020] The seventh invention is, in the above invention, The direction of one end is defined as the direction along the rail, and the predetermined range of the track is defined as the detection range. It is a radar device.

[0021] According to the seventh invention, the direction of the antenna's front, which is one end direction, is aligned with the rail, making it possible to realize a radar device for detecting obstacles within a detection range which is a predetermined range of the railway track. [Brief explanation of the drawing]

[0022] [Figure 1] An example of radar equipment installation. [Figure 2] Diagram showing the configuration of a radar system. [Figure 3] A diagram illustrating the design procedure for a radome. [Figure 4] A diagram illustrating the design procedure for a radome. [Figure 5] A diagram illustrating the design procedure for a radome. [Figure 6] A diagram illustrating the range of radio wave transmission. [Figure 7] A diagram illustrating the radio wave reception range. [Figure 8] Experimental results using the radar device of this embodiment. [Figure 9] Experimental results using the radar device of this embodiment. [Figure 10] Experimental results using a comparative radar device. [Figure 11] Experimental results using a comparative radar device. [Figure 12]Experimental results using this embodiment and a comparative radar device. [Figure 13] A torture of a radome. [Figure 14] Other examples of radar equipment installations. [Modes for carrying out the invention]

[0023] Preferred embodiments of the present invention will be described below with reference to the drawings. However, the applicable forms of the present invention are not limited to the following embodiments. Furthermore, in the drawings, the same elements are denoted by the same reference numerals.

[0024] [Example of radar equipment installation] Figure 1 shows an example of the installation of the radar device 1 in this embodiment. In Figure 1, the coordinate system used to represent direction is an XYZ Cartesian coordinate system, where the direction in front of the radar device 1 is the positive X-axis, the direction towards the railway line as seen from the radar device 1 is the positive Y-axis, and the direction vertically upward is the positive Z-axis. Furthermore, the direction as seen from the radar device 1 is also referred to as forward (positive X-axis), right (positive Y-axis), left (negative Y-axis), upward (positive Z-axis), and downward (negative Z-axis).

[0025] As shown in Figure 1, the radar device 1 (1a, 1b) of this embodiment detects the presence or absence of an object within its detection range by transmitting and receiving radio waves, and constitutes part of an obstacle detection device installed near railway tracks to detect obstacles within the tracks. Specifically, multiple radar devices 1 are installed near the tracks at predetermined intervals or at arbitrary locations. The radar device 1 is installed with its forward direction (positive X-axis direction) substantially aligned with the direction along the rails, and a predetermined range including the tracks in front is associated with the detection range 3 (3a). In the example in Figure 1, the detection range 3a is defined as the range including the tracks to the front right as viewed from radar device 1a. Furthermore, the radar device 1 of this embodiment scans a horizontal plane at a predetermined height from the ground by transmitting and receiving radio waves while changing the transmission direction within a predetermined detection angle range. The detection range 3 associated with the radar device 1 is determined to be included within the detection angle range scanned by the radar device 1.

[0026] [Radar equipment] Figure 2 shows the configuration of the radar device 1. Figure 2 shows a schematic end view of the radar device 1, with the top of the drawing being the front direction (positive X-axis direction) and the right direction of the drawing being the positive Y-axis direction (rightward direction). The radar device 1 comprises an antenna unit 10 and a radome 20 that houses the antenna unit 10. The antenna unit 10 constitutes a MIMO (Multi Input Multi Output) antenna, with a transmitting unit 14, which is a transmitting antenna array, and a receiving unit 16, which is a receiving antenna array, mounted on a substrate 12.

[0027] The radome 20 restricts the detection angle range of the radar device 1 to a portion of the detection angle range (field of view) of the antenna unit 10 alone. Specifically, the detection angle range of the antenna unit 10 alone is a predetermined angle range with approximately equal angles in the left and right directions (Y-axis direction) centered on its front direction (antenna front direction: positive X-axis direction), but the range on the opposite side (left side: negative Y-axis direction) from where the center of the detection range is located relative to the front direction is restricted. In other words, the detection angle range of the radar device 1 is biased toward the side of the detection range (right side: positive Y-axis direction) relative to the antenna front direction (positive X-axis direction).

[0028] The radome 20 has a convex shape in the direction of the front of the antenna, so as to cover the flat surface on which the antenna section 10 is provided, and its outer shape is formed to resemble a semi-circular shape.

[0029] The antenna unit 10 has a substrate 12 on which a transmitting unit 14 and a receiving unit 16 are arranged on a plate surface. When viewed from the front, which is the opposite direction from the front of the antenna, the transmitting unit 14 is positioned behind the convex top portion of the radome 20. Furthermore, the positions of the transmitting unit 14 and the receiving unit 16 are separated in the direction normal to the front of the antenna (Y-axis direction), and the receiving unit 16 is located on the opposite side (left side) from the detection range relative to the transmitting unit 14. More specifically, the transmitting unit 14 is located behind the convex top portion, and behind the transparent portion 22 (more precisely, behind the approximate central portion of the transparent portion 22) which is provided on the top portion, while the receiving unit 16 is located in an off-center position on the opposite side (left side) from the detection range relative to the transmitting unit 14. The schematic end view in Figure 2 can also be described as a side view perpendicular to the front of the antenna and the direction normal to the front of the antenna.

[0030] The radome 20 is made entirely of dielectric material and has a radio wave-transmitting portion 22 located at the top of the convex portion and a radio wave-absorbing portion 24 located around the top portion that absorbs radio waves.

[0031] The thickness d1 of the transmission portion 22 and the absorption portion 24 is an integer multiple of half the wavelength of the radio waves transmitted and received by the antenna portion 10, as shown in equation (1). This thickness d1 is the thickness that minimizes the loss of traveling waves incident perpendicularly to the transmission portion 22. Here, the wavelength λm is the wavelength of the radio waves as they pass through the radome 20, and is determined by the relative permittivity εr of the dielectric material forming the radome 20, as shown in equation (2).

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[0032] The general configuration of the transmission section 22 and the absorption section 24 will be described first. The transmission section 22 is formed in a flat plate shape perpendicular to the direction of the front of the antenna. The width of the transmission section 22, which is the length along the normal direction to the direction of the front of the antenna (the direction parallel to the substrate 12 of the antenna section 10: the Y-axis direction), is greater than the width of the substrate 12. In detail, in Figure 2, the end of the transmission section 22 on the side opposite to the detection range (left side) and the end of the receiving section 16 on the side opposite to the detection range (left side) are in roughly the same position in the Y-axis direction.

[0033] The absorption section 24 is formed in the shape of an arc-shaped curved surface centered on the installation position of the transmission section 14. The diameter of this curved surface is larger on the side of the receiving section 16's installation position relative to the transmission section 14 (the diameter of arc R1 in Figures 4 and 5, described later) than on the second diameter on the opposite side of the receiving section 16's installation position relative to the transmission section 14 (the diameter of arc R2 in Figures 4 and 5, described later). In other words, the diameter on the opposite side (left side) of the detection range is larger.

[0034] Furthermore, the absorption section 24 includes a plate-shaped reflective member 26 at a distance d2 from the inner surface, which reflects the radio waves transmitted and received by the antenna section 10. The distance d2 is the distance at which the phase of the reflected wave differs by 180 degrees from that of the incident wave incident perpendicularly to the inner surface of the absorption section 24, as shown in equation (3).

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[0035] [How to design a radome] Next, the detailed configuration of the radome 20, including the transmission section 22 and the absorption section 24, will be described. Figures 3 to 5 illustrate the design procedure of the radome 20. However, it is assumed that the radar device 1 is installed so that its detection range is to the right of the antenna's front direction, and that its installation position and orientation are predetermined.

[0036] First, as shown in Figure 3, lines L1 and L2 are determined such that the detection range of the radar device 1 is included within the recommended detection angle range, which is defined as the range between line L1, which is in the direction of one end, and line L2, which is in the direction of the other end. That is, line L1 is drawn passing through the end of the substrate 12 of the antenna unit 10 on the side of the receiving unit 16 (left side relative to the front direction of the antenna) and in the direction toward the detection range along the rail. Also, line L2 is drawn passing through the end of the substrate 12 of the antenna unit 10 on the side of the transmitting unit (right side relative to the front direction of the antenna) and in the direction toward the detection range, and the detection range is included within the range between line L1 and line L2. The angle formed by line L1 and line L2 is the recommended detection angle range. These lines L1 and L2 are determined by the distance and angle from the estimated design installation position of the radar device 1 to the estimated design detection range as seen. Next, line segment L3 corresponding to the transmission part 22 is drawn, connecting the intersection points Q1 and Q2 of the line parallel to the substrate 12 of the antenna unit 10 and lines L1 and L2, respectively. The length of line segment L3 is greater than the width of the substrate of the antenna section 10.

[0037] Next, draw a circle C1 centered at the position of the transmitter 14, passing through the intersection point Q1 of line L1 and line segment L3. Also, draw a circle C2 centered at the position of the transmitter 14, passing through the intersection point Q2 of line L2 and line segment L3. Since the distance from the position of the transmitter 14 to intersection point Q1 is longer than the distance to intersection point Q2, the radius of circle C1 (the first diameter) is longer than the radius of circle C2 (the second diameter). In other words, circle C1 is larger than circle C2.

[0038] Next, as shown in Figure 4, the inner surface of the radome 20 is determined. That is, a line segment L4 is drawn connecting the intersection points Q3 and Q4 of the straight line parallel to the substrate 12 of the antenna section 10 with circles C1 and C2, respectively. The surface formed by line segment L3, the arc R1 of circle C1 between intersection points Q3 and Q1, and the arc R2 of circle C2 between intersection points Q2 and Q4 is defined as the inner surface of the radome 20. Line segment L3 corresponds to the inner surface of the transmission section 22, and arcs R1 and R2 correspond to the inner surfaces of the absorption section 24.

[0039] Of the two intersection points Q1 and Q2 that form the boundary between the penetrating section 22 and the absorbing section 24, intersection point Q1 is further from the transmitting section 14 of the antenna section 10 than intersection point Q2. Therefore, the diameter of the curved surface on the inner surface of the absorbing section 24 is such that the diameter of the first diameter, arc R1, on the side of the receiving section 16's installation position relative to the transmitting section 14 is greater than the diameter of the second diameter, arc R2, on the side opposite to the receiving section 16's installation position relative to the transmitting section 14.

[0040] Next, as shown in Figure 5, the position at a distance d1 outward from the inner surface of the determined radome 20 is determined as the outer surface of the radome 20. Then, for the absorption section 24, a reflective member 26 is provided at a position at a distance d2 from its inner surface.

[0041] Figure 6 is a diagram showing an overview of the range of radio waves (transmitted waves) transmitted from the radar device 1, and Figure 7 is a diagram showing an overview of the range of radio waves (received waves; reflected waves) received by the radar device 1. As shown in Figure 6, the transmitting unit 14 of the antenna unit 10 transmits radio waves in the direction of the detection angle range of the transmitting unit 14 alone (a range of approximately equal angles in the left and right directions centered on the direction in front of the antenna).

[0042] Of these radio waves, those directed towards the radome's penetrating section 22 are transmitted to the outside of the radar device 1 by passing through the penetrating section 22, as indicated by the solid arrows.

[0043] On the other hand, radio waves heading towards the absorption section 24 are absorbed by the absorption section 24, as indicated by the dashed arrow. That is, since the inner surface of the absorption section 24 is an arc centered on the transmitting section 14, radio waves heading from the transmitting section 14 to the absorption section 24 are incident perpendicular to the absorption section 24. The radio waves incident on the absorption section 24 (incident waves) are reflected by the reflecting member 26 inside the absorption section 24. However, since the distance d2 from the inner surface of the absorption section 24 is such that the phase of the reflected wave is 180 degrees different from that of the incident wave incident perpendicular to the inner surface of the absorption section 24, the incident and reflected waves cancel each other out and are absorbed. In other words, by incident perpendicularly to the absorption section 24, the radiation of radio waves outside the antenna in the direction from the transmitting section 14 to the absorption section 24 is efficiently suppressed.

[0044] Therefore, the radio waves (transmitted waves) transmitted from the transmitting unit 14 of the antenna unit 10 are basically transmitted to the outside only from the penetrating unit 22. The transmission range is defined as the angular range between the transmitting unit 14 and each end of the penetrating unit 22. This angular range is wider than the recommended detection angle range defined as the range between the straight lines L1 and L2.

[0045] On the other hand, as shown in Figure 7, of the radio waves (reflected waves) that travel from the outside toward the radar device 1, the radio waves that travel toward the penetrating section 22, as indicated by the solid arrows, pass through the penetrating section 22 and enter the interior of the radome 20, where they are received by the receiving section 16 of the antenna section 10.

[0046] As shown by the dashed arrows in Figure 7, radio waves directed towards the absorption section 24 are absorbed or reflected by the absorption section 24 and do not enter the interior of the radome 20. In other words, radio waves from the outside are reflected by the reflecting member 26 inside the absorption section 24, and the distance d from the outer surface of the absorption section 24 to the reflecting member 26 is d = d1 - d2 = λm / 4. Therefore, radio waves incident perpendicular to the surface of the absorption surface (incident waves) have a phase difference of 180 degrees with the reflected waves at the reflecting member 26, and they cancel each other out and are absorbed, while other radio waves are partially absorbed.

[0047] Thus, the radio waves (received waves) received by the receiving section 16 of the antenna section 10 are only those that pass through the transmission section 22. The reception range is defined as the angular range between the receiving section 16 and each end of the transmission section 22. This roughly coincides with the recommended detection angular range defined as the range between the straight lines L1 and L2.

[0048] [Experimental Results] This section describes the experimental results using the radar device 1 of this embodiment. The experiment was conducted by installing the radar device 1 near a railway test track and simulating the detection of obstacles on the tracks. As shown in Figure 1, the radar device 1 was installed with its front direction (antenna front direction) aligned with the rails, and the detection range was defined as the track to the right of the front direction. Experiments were conducted with and without obstacles to be detected within the detection range. The obstacles were placed at a distance of 11 m from the radar device 1. In addition, for comparison with the radar device 1 of this embodiment (hereinafter referred to as "with radome"), experiments were similarly conducted with and without obstacles using a radar device consisting only of the antenna section 10 (hereinafter referred to as "without radome").

[0049] Figures 8 and 9 show the experimental results of the radar device 1 (with radome) of this embodiment. Figure 8 is a graph showing the relationship between distance and received power, with the horizontal axis representing the distance from the radar device 1 and the vertical axis representing the received power at the radar device 1. Received power is the sum of the power of the reflected waves received by the radar device 1. The solid line graph shows the experimental results with obstacles, and the dashed line graph shows the experimental results without obstacles. Comparing the results of both experiments, it can be seen that there is a difference in received power around distances of 11m and 24-40m.

[0050] Figure 9 is a graph obtained from the experimental results in Figure 8, and it shows the signal-to-noise ratio (SNR) calculated by considering the experimental results when there are no obstacles within the detection range as background noise. In Figure 9, the horizontal axis is the distance from the radar device and the vertical axis is the SNR, showing the relationship between distance and SNR. According to Figure 9, there are SNR peaks at several points, and these peaks correspond to the distances where some kind of object is present. Of these peaks, the peak value at a distance of 11m, where an obstacle was placed, is larger than the peak values ​​at other distances.

[0051] Figures 10 and 11 show the experimental results using a comparative radar device (without a radome). In Figure 10, similar to Figure 8, the horizontal axis represents the distance from the radar device, and the vertical axis represents the received power at the radar device, showing the relationship between distance and received power as a graph. The solid line graph represents the experimental results with obstacles within the detection range, while the dashed line graph represents the experimental results without obstacles.

[0052] Figure 11 is a graph obtained from the same experimental results as in Figure 9, and it represents the SNR obtained by considering the experimental results when there are no obstacles within the detection range as background noise. In Figure 11, the horizontal axis is the distance from the radar device and the vertical axis is the SNR, showing the relationship between distance and SNR.

[0053] As shown in Figure 11, there are SNR peaks at several locations, including at a distance of 11m where the obstacle is placed. In particular, the SNR peak at a distance of 34m is due to multipath noise, but it is larger than the SNR peak at 11m where the obstacle is placed, which could lead to false detection of the obstacle.

[0054] The experimental results for the comparative radar device (without radome) shown in Figure 11 are compared with the experimental results for the radar device 1 (with radome) of this embodiment shown in Figure 9. The peak SNR value due to an obstacle at a distance of 11m is approximately 6dB for the radar device 1 (with radome) of this embodiment, which is larger than the approximately 4dB for the comparative radar device (without radome). This is because background noise is suppressed by the radome 20, as will be described later. Furthermore, the peak SNR value at a distance of 34m due to an object outside the detection range is approximately 0.5dB for the radar device 1 (with radome) of this embodiment, which is considerably smaller than the approximately 6dB for the comparative radar device (without radome). In other words, it can be said that noise due to multipath is suppressed by the radome 20. In addition, other peaks that appeared in the comparative radar device (without radome) are also smaller in the radar device 1 (with radome) of this embodiment.

[0055] Figure 12 shows the experimental results when there are no obstacles within the detection range. In Figure 12, as with Figures 8 and 10, the horizontal axis represents the distance from the radar device and the vertical axis represents the received power at the radar device, showing the relationship between distance and received power as a graph. The solid line graph shows the experimental results for radar device 1 (with radome) of this embodiment, and the dashed line graph shows the experimental results for a comparative radar device (without radome).

[0056] As shown in Figure 12, overall, the radar device 1 (with radome) of this embodiment has lower received power compared to the comparative radar device (without radome). This is because, in the radar device 1 (with radome) of this embodiment, the reception of radio waves from outside the detection range is limited by the radome 20. In other words, background noise is suppressed.

[0057] [Effects and Effects] According to this embodiment, it is possible to realize a radar device 1 equipped with a radome 20 that suppresses the reception of reflected waves from objects outside the detection range. The transmitting unit 14 and the receiving unit 16 of the antenna unit 10 are positioned apart in the direction normal to the front direction of the antenna, and in a front view which is opposite to the front direction of the antenna, the transmitting unit 14 is located behind the top portion of the radome 20 or the central portion of the transmissive unit 22. Therefore, by installing the radar device 1 such that the direction of the positional displacement of the receiving unit 16 relative to the transmitting unit 14 corresponds to the direction of the detection range which is biased relative to the front direction of the antenna, the direction of transmission and reception of radio waves is generally restricted to the direction of the detection range. This makes it possible to suppress the reception of reflected waves from objects outside the detection range that are received by the radar device 1.

[0058] [Differentiation] It should be noted that the applicable embodiments of the present invention are not limited to those described above, and can be modified as appropriate without departing from the spirit of the invention.

[0059] (A) Shape of the transparent part The shape of the transparent portion 22 of the radome 20 may be a curved shape, for example, as shown in Figure 13. In this case, it is preferable to create the inner surface of the transparent portion 22 as an arc centered on the position of the transmitting portion 14 of the antenna portion 10.

[0060] (B) Installed near the level crossing The radar device 1 can also be used as an obstacle detection device to detect obstacles within a level crossing. Specifically, as shown in Figure 14, two radar devices 1a and 1b are installed near the level crossing 5, between the uphill and downhill tracks, with the level crossing 5 as their detection range. One radar device 1a is installed on the uphill track side with its front facing the rails, and its detection range 3a is set to the uphill track side of the level crossing 5. The other radar device 1b is installed on the downhill track side with its front facing the rails, and its detection range 3b is set to the downhill track side of the level crossing 5.

[0061] (C) Application to non-railway applications The radar device 1 can be applied to uses other than railways. For example, in a pedestrian crossing on a straight road with a pedestrian signal, the radar device 1 can be installed on the side of the road so that its front direction is aligned with the pedestrian crossing. The radar device 1 can then be applied to detect pedestrians left behind on the pedestrian crossing when the pedestrian signal changes from green to red. When a pedestrian left behind on the pedestrian crossing is detected, it is preferable to perform predetermined countermeasures such as emitting a warning sound or delaying the timing of changing the traffic signal for cars on the straight road to green. [Explanation of Symbols]

[0062] 1... Radar equipment 10… Antenna section 12… Circuit board 14…Transmitter 16... Receiver 20... Radome 22…Transparent part 24… Absorbent part 26…Reflective material 3…Detection range 5... railroad crossing

Claims

1. A radar device that detects the presence or absence of an object within its detection range by transmitting and receiving radio waves, An antenna unit having a transmitting unit and a receiving unit located at separate positions in the direction normal to the front direction of the antenna, The radome having a convex shape in the direction of the front of the antenna, Equipped with, The aforementioned radome is A transparent section that transmits radio waves is provided at the top, An absorbing section for absorbing radio waves is provided in the peripheral portion of the aforementioned top portion, It has, The transmitting unit is located behind the top portion or behind the transparent portion when viewed from the front, which is in the opposite direction to the front of the antenna. Radar device.

2. The detection range is included in a planar recommended detection angle range defined by the direction of one end and the direction of the other end, with the direction along the front of the antenna being one end direction. The antenna section is positioned such that, in a side view perpendicular to the front direction and the normal direction of the antenna, the side of the receiving section's installation position relative to the transmitting section and the side of the other end relative to the one end are opposite, with the transmitting section and the receiving section separated from each other. The radar device according to claim 1.

3. The receiving unit is located behind the transparent section in the front view. The radar device according to claim 2.

4. The inner surface of the absorption section is an arc-shaped curved surface centered on the installation position of the transmission section. A radar device according to any one of claims 1 to 3.

5. The inner surface of the absorption section is an arc-shaped curved surface centered on the installation position of the transmission section. The diameter of the curved surface is such that the first diameter on the side of the receiving unit's installation position relative to the transmitting unit is greater than the second diameter on the side opposite to the receiving unit's installation position relative to the transmitting unit. The radar device according to claim 2 or 3.

6. The thickness of the transmitting portion and the absorbing portion is an integer multiple of half the wavelength of the radio wave. The absorption section contains a reflective member that reflects radio waves at a distance from the inner surface such that the phase of the reflected wave is 180 degrees different from that of the incident wave to the reflective member. A radar device according to any one of claims 1 to 3.

7. The radar device according to claim 2 or 3, wherein the direction of one end is the direction along the rail and the detection range is a predetermined range of the railway track.

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