JP2010096650A - Radar system - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a radar system capable of detecting an object the height above ground level of which is low, while averting reception of reflected waves of electromagnetic wave beams that are emitted from its antennas and reflected by the ground surface. <P>SOLUTION: The individual antennas 11-13 emit the electromagnetic wave beams B1-B3 spreading into the shape of sectors, and receive the reflected waves of the electromagnetic wave beams reflected by an object to be detected 3, and the antennas are piled up vertically, one by one, and are at predetermined heights h1-h3 from the ground surface 4. With respect to each of the antennas 11-13, when the height above the ground surface 4 of the object 3 is represented as H (m), and the distance from the antenna 11-13 up to the object 3 is represented as R (m), the lowest edge of the sector of the electromagnetic wave beam B1-B3 emitted by the antenna itself does not exceed the height H, above the ground surface within the range of the distance R, and all the antennas have elevation angles θ1 to θ3, capable of preventing waves reflected by the ground surface 4 from being received and contained in received reflected waves. <P>COPYRIGHT: (C)2010,JPO&INPIT

Description

  The present invention relates to a radar apparatus that radiates an electromagnetic wave beam and receives a reflected wave from a detected object and detects the distance to the detected object or the presence or absence of the detected object.

  In recent years, the development and utilization of electromagnetic waves in the millimeter wave band (30 to 300 GHz) has become rapidly active. One of its uses is in the field of sensing, such as a collision prevention radar device, a radar device related to ITS (Intelligent Transport Systems), and a radar device for position measurement and control of a mobile robot. Furthermore, a radar device in an obstacle detection system at a railroad crossing is known. As an example of a radar apparatus using millimeter waves, a ranging radar apparatus disclosed in Patent Document 1, a railroad crossing obstacle detection radar apparatus disclosed in Patent Document 2, and the like are known.

  The radar devices using millimeter waves are effective in these systems because they have characteristics such as high angular resolution, small and lightweight equipment, and the ability to propagate even in media that do not transmit light. In addition, there is an advantage that oxygen molecules are absorbed in the vicinity of 60 GHz, interference at a slightly distant place is eliminated, and the same frequency can be reused.

  However, there are various objects to be detected which are the detection targets of the radar apparatus, and generally, not only the shape, such as an automobile, a bicycle, a person, a structure, etc., but also the ground height differs from one area to another. In addition, the distances from the radar device to these objects to be detected are variously different.

Under these circumstances, if an object with a low height above the ground is detected, the electromagnetic wave beam radiates in a fan shape from the antenna, causing a reflected wave that is reflected from the ground, which is received by the antenna. Will result in erroneous detection output. In order to avoid such erroneous detection, it is necessary to match an object with a high height above the ground, and it is inevitably impossible to detect a low object.
JP 2007-333539 A JP-A-2005-231461

  An object of the present invention is to provide a radar device that can detect an object having a low ground height while avoiding reception of a ground reflected wave of an electromagnetic wave beam radiated from an antenna.

In order to solve the above-described problem, a radar apparatus according to the present invention includes a plurality of antennas. Each of the antennas emits an electromagnetic beam having a fan-shaped spread and receives a reflected wave of the electromagnetic wave beam reflected by the object to be detected, and is sequentially stacked vertically to a predetermined height from the ground. positioned. In the above configuration, when the height of the detected object from the ground is H (m) and the distance from the antenna to the detected object is R (m),
In any of the antennas, the sector-shaped lowermost edge of the electromagnetic wave beam radiated by the antenna does not exceed the ground height H within the range of the distance R, and the reflected wave reflected by the ground on the received reflected wave. Has an elevation angle that does not include

  As described above, in any of the antennas, the fan-shaped bottom edge of the electromagnetic wave beam radiated by itself does not exceed the ground height H within the range of the distance R. An object of H or more can be reliably detected. That is, at least a low object having a ground height H can be reliably detected. The distance R is the maximum distance at which the object can be detected stably in the radar device.

  In addition, since any of the antennas has an elevation angle that does not include the reflected wave reflected by the ground in the received reflected wave, an erroneous detection operation caused by the reflected wave reflected by the ground can be avoided. .

  Specifically, the elevation angle of the electromagnetic wave beam is larger for the plurality of antennas as the antenna is located on the lower side in the vertical stack. By doing so, it is possible to reliably avoid the erroneous detection operation caused by the reflected wave reflected on the ground in the lower antenna that is likely to be reflected on the ground.

  In the radar apparatus according to the present invention, the electromagnetic wave beam is preferably a millimeter wave. As a result, it has the advantages of millimeter waves, that is, high angular resolution, small and lightweight equipment, and the ability to propagate even in media that does not transmit light, and there is no interference at a little distance, It is possible to realize a radar apparatus having advantages such as being able to reuse the same frequency.

  As described above, according to the present invention, it is possible to provide a radar apparatus that can detect an object having a low ground height while avoiding reception of a ground reflected wave of an electromagnetic wave beam radiated from an antenna.

  Other features of the present invention and the operational effects thereof will be described in more detail by way of examples with reference to the accompanying drawings.

  FIG. 1 is a diagram for explaining an antenna arrangement of a radar apparatus according to the present invention. The illustrated radar apparatus includes a plurality of n antennas 11 to 13 and a signal processing apparatus 2. The number of antennas 11 to 13 is n = 3 in the drawing, but may be more than that or two. Each of the antennas 11 to 13 emits the electromagnetic wave beams B1 to B3 having a fan-shaped spread and receives the reflected waves of the electromagnetic wave beams B1 to B3 reflected by the detection target 3, and sequentially stacks vertically. And located at a predetermined height h1 to h3 from the ground 4.

  The electromagnetic waves B1 to B3 have a main lobe that spreads in a fan shape at a certain solid angle from the radiation surface of the antennas 11 to 13 toward the front. In the figure, in the electromagnetic wave beams B1 to B3 having such characteristics, the effective detection area is shown as an electromagnetic wave beam divided by a half-value angle (3.0 dB lowering point) area.

  As for the vertically stacked antennas 11 to 13, the antenna 11 located at the uppermost part has a height h1, the antenna 13 located at the lowermost part has a height h3, and the antenna 12 located in the middle part with respect to the ground 4 It is at the position of height h2. The antennas 11 to 13 may be installed on a fixed structure provided on the ground 4 or may be mounted on a moving body such as an automobile.

  Various types of antennas 11 to 13 have been proposed. Among them, what is called a slot array antenna in which a large number of antenna elements are aligned is preferable.

  The object 3 to be detected may be a moving object or a fixed reflector. The moving object is, for example, an automobile, a bicycle, a human, a moving structure, or the like. The reflector may be used as a monitor for monitoring electromagnetic wave radiation of the antennas 11 to 13 when configuring an obstacle detection device at a railroad crossing, for example.

  The signal processing unit 2 decodes the signals supplied from the antennas 11 to 13, calculates the distance and presence of the detected object 3, and outputs them.

  In the above configuration, when the ground height of the detected object 3 from the ground 4 is H (m) and the distance from the antennas 11 to 13 to the detected object 3 is R (m), any of the antennas 11 to 13 is selected. However, the fan-shaped lowermost edge of the electromagnetic wave beams B1 to B3 emitted by itself does not exceed the ground height H within the range of the distance R, and the reflected wave reflected by the ground 4 is not included in the received reflected wave. It has elevation angles θ1 to θ3. The distance R is the maximum distance at which the object can be detected stably in the radar apparatus.

  As described above, in any of the antennas 11 to 13, the fan-shaped bottom edge of the electromagnetic wave beams B <b> 1 to B <b> 3 that the antenna radiates does not exceed the ground height H within the range of the distance R. It is possible to reliably detect an object having a height above ground level H. That is, at least the low detection object 3 having the ground height H can be reliably detected.

  In addition, since each of the antennas 11 to 13 has the elevation angles θ1 to θ3 in which the reflected wave reflected by the ground 4 is not included in the received reflected wave, erroneous detection caused by the reflected wave reflected by the ground 4 is avoided. be able to.

  Specifically, in the plurality of antennas 11 to 13, the elevation angles of the electromagnetic wave beams B <b> 1 to B <b> 3 are larger as the antennas 11 to 13 located on the lower side in the vertical stack. That is, θ1 <θ2 <θ3. By doing so, it is possible to reliably avoid the erroneous detection operation caused by the reflected wave reflected by the ground 4 in the lower antennas 11 to 13 that are easy to receive the reflected wave from the ground 4.

As a specific example, when R = 25 m and H = 0.60 m,
θ1 = 0.0 °
θ2 = 0.344 °
θ3 = 0.688 °
Set as follows. In the illustrated embodiment, the height h1 of the antenna 11 located at the top (height seen at the beam radiation center position) is made to coincide with the ground height H of the object 3 to be detected, Since it is the height h2 and the height h3 of the lowermost antenna 13,
^{θ1 = Tan - (H-h1} ) /R=0.0°
^{θ2 = Tan - (H-h2} ) /R=0.344°
^{θ3 = Tan - (H-h3} ) /R=0.688°
It becomes.

  Such a relationship between the distance R, the height H, h1 to h3, and the elevation angles θ1 to θ3 is useful in a crossing obstacle detection system. This is because it is possible to detect a level crossing obstacle (detected object 3) having a ground height of H0.6 m while avoiding reception of reflected ground waves of the electromagnetic waves B1 to B3 radiated from the antennas 11 to 13. However, the distance R, height H, h1 to h3, and elevation angles θ1 to θ3 change according to the application of the radar system, and are not fixed values.

  In the radar apparatus according to the present invention, the electromagnetic beams B1 to B3 are preferably millimeter waves. Accordingly, it is possible to realize a radar apparatus having the advantages of millimeter waves, that is, characteristics such as high angular resolution, small and light equipment, and propagation in a medium that does not transmit light. In addition, when millimeter waves near 60 GHz are used as the electromagnetic beams B1 to B3, absorption by oxygen molecules occurs near 60 GHz, and there is no interference at a slightly distant place, and the same frequency can be reused. .

  While the present invention has been described with reference to the embodiment, it is needless to say that the present invention is not limited to this embodiment, and various modifications and changes can be made within the scope of the claims.

It is a figure explaining the antenna arrangement | positioning of the radar apparatus which concerns on this invention.

Explanation of symbols

11-13 Antenna
2 Signal processor
3 Object to be detected
4 Ground B1-B3 Electromagnetic beam

Claims (4)

A radar device including a plurality of antennas,
Each of the antennas emits an electromagnetic beam having a fan-shaped spread and receives a reflected wave of the electromagnetic wave beam reflected by the object to be detected, and is sequentially stacked vertically to a predetermined height from the ground. Yes,
When the ground height of the detected object from the ground is H (m) and the distance from the antenna to the detected object is R (m),
In any of the antennas, the fan-shaped lowermost edge of the electromagnetic wave beam radiated by itself does not exceed the ground height H within the range of the distance R, and is reflected by the reflected wave to be received by the ground. Has an elevation angle that does not include reflected waves,
Radar device.   2. The radar apparatus according to claim 1, wherein the plurality of antennas have a higher elevation angle of the electromagnetic wave beam as the antenna is located on the lower side in the vertical stack.   3. The radar apparatus according to claim 1, wherein, among the plurality of antennas, the antenna at the top in the vertical stack has a fan-shaped bottom edge of the electromagnetic wave beam radiated by a ground height H. A radar device that matches   The radar apparatus according to any one of claims 1 to 3, wherein the electromagnetic wave beam is a millimeter wave.

Images