JP2010204032A - Radar device for vehicle - Google Patents

Abstract

An antenna beam is efficiently squeezed toward a target while suppressing clutter from the vehicle lower direction.
An antenna unit 20 comprising an antenna substrate on which an antenna element is printed and an antenna spacer 12 has a distance between the antenna element 11 and a vehicle body frame that is ¼ of the wavelength λ of the center frequency of the antenna band. Install as follows. Further, a reflector unit 21 comprising a flat reflector 22 and a reflector spacer 23 for mounting on the vehicle body is disposed below the antenna unit 20, and the distance between the antenna element 11 and the reflector 22 is also set to λ / 4. As a result, the antenna beam can be efficiently narrowed toward the target while suppressing clutter from the vehicle lower direction.
[Selection] Figure 6

Description

  The present invention relates to a vehicular radar apparatus that detects an object existing around a vehicle.

  2. Description of the Related Art In recent years, vehicles such as automobiles are equipped with radars, cameras, and the like to detect objects existing around the host vehicle and use them for collision prevention, auto cruise traveling control, and the like. In this case, in order to detect an object around the vehicle, it is necessary to arrange radars and cameras at a plurality of locations on the vehicle body.

  An example of such an arrangement on the vehicle body is disclosed in Patent Document 1, for example. Patent Document 1 discloses a periphery monitoring system in which a camera and a radar device are attached to the left and right side surfaces of a vehicle to detect an obstacle present on the side.

JP 2008-52399 A

  However, in the above-described Patent Document 1, no consideration is given to the transmission / reception efficiency of the antenna itself of the radar device and the interference with the antenna due to clutter (random scattering) from the ground.

  For this reason, in order to accurately detect the target by actually mounting the radar apparatus on the vehicle, it is necessary to overcome the problems of improving the transmission / reception efficiency of the antenna and preventing clutter from the ground in the lower part of the vehicle.

  The present invention has been made in view of the above circumstances, and an object of the present invention is to provide a vehicular radar device capable of efficiently narrowing an antenna beam toward a target while suppressing clutter from the vehicle lower direction.

  In order to achieve the above object, a vehicle radar device according to the present invention is a vehicle radar device that is mounted on a vehicle and detects an object existing around the vehicle by transmitting and receiving radar waves, and is attached to a vehicle body frame. An antenna and a reflector attached to the lower part of the antenna for reflecting radio waves, and the distance between the antenna element of the antenna and the body frame, and the distance between the antenna element and the reflector, It arrange | positions so that it may become in the predetermined range centering on 1/4 of the wavelength of center frequency.

  According to the present invention, it is possible to efficiently narrow the antenna beam toward the target while suppressing clutter from the ground or the like below the vehicle.

System configuration diagram of vehicle radar device Explanatory drawing showing the arrangement of units as seen from the top of the car Explanatory drawing showing the arrangement of units as seen from the side of the car Plan view of antenna unit Side view of antenna unit Plan view of antenna unit and reflector unit Explanatory drawing showing the positional relationship between the antenna and the vehicle body Explanatory drawing showing installation of antenna to lower part of door Explanatory drawing showing the beam pattern in the vertical direction when there is no reflector Explanatory drawing showing the beam pattern in the vertical direction when the reflector is mounted Explanatory drawing showing the relationship between antenna arrangement and lateral beam pattern

Embodiments of the present invention will be described below with reference to the drawings.
In FIG. 1, reference numeral 1 denotes a vehicle radar device (hereinafter simply referred to as “radar device”) that measures the distance to an object that is mounted on a vehicle such as an automobile and exists around the vehicle. The radar apparatus 1 includes a plurality of radar units 5 having a transmission antenna 2a, a reception antenna 2b, and a radar board 3 on which signal processing circuit components are mounted, a control unit 50 for controlling the plurality of radar units 5, and a control unit 50. Are provided with a plurality of alarm units 55 connected to each other. In the present embodiment, there are 8 sets of radar units 5 and 2 sets of alarm units.

  The control unit 50 supplies a power supply ACC to each radar unit 5 and the alarm unit 55 and outputs a ranging request signal to each radar unit 5. Receiving the distance measurement request signal, each radar unit 5 transmits a transmission wave from the transmission antenna 2a, receives the reflected wave reflected by the object by the reception antenna 2b, performs distance measurement processing, and transmits the distance measurement signal to the control unit. 50.

  When receiving the distance measurement signal from each radar unit 5, the control unit 50 performs an alarm process or the like according to the distance from the detected object. The control unit 50 determines the possibility of contact between the detected object and the host vehicle, and outputs a warning signal to the warning unit 55 to give a warning to the driver when it is determined that there is a possibility of contact.

  The control unit 50 is connected to an in-vehicle network based on a communication protocol such as CAN (Controller Area Network). Other in-vehicle electronic devices are connected to the in-vehicle network, and the control unit 50 communicates with the other electronic devices and exchanges various information with each other.

  2 and 3 show examples of arrangement of units of the radar apparatus 1 mounted on the automobile 100. FIG. The radar unit 5 has two left and right corner portions inside the front bumper 101 and two left and right corner portions inside the rear bumper 102, two left and right portions below the front door 103, and two left and right corners below the rear door 104, for a total of eight. It is arranged at the place.

  On the other hand, the control unit 50 is installed on the floor under the seat on the left side in the traveling direction in the passenger compartment, and is connected to each radar unit 5 and the alarm unit 55. The alarm unit 55 is embedded in the left and right front pillars 105 and has a configuration in which a plurality of warning lights are exposed in the passenger compartment.

  The transmission antenna 2a and the reception antenna 2b of each radar unit 5 are a pair of antennas having the same shape, and the transmission antenna 2a and the reception antenna 2b constituting the pair are arranged at a predetermined interval. Hereinafter, the transmitting antenna 2a and the receiving antenna 2b are representatively described as the antenna 2.

  As shown in FIG. 4, the antenna 2 has antenna elements 11 a. 11b is a broadband dipole antenna formed by printing 11b. The antenna elements (dipole elements) 11a and 11b have an antenna length that is ½ of the wavelength λ of the center frequency of the antenna band, and a feeding point 11c is provided at substantially the center. An antenna substrate 10 on which the antenna elements 11a and 11b (hereinafter, the antenna elements 11a and 11b are collectively referred to as the antenna element 11) is fixed to an antenna spacer 12 made of a nonconductive material such as a resin, The unit 20 is attached to the vehicle body.

  As shown in FIG. 5, the antenna spacer 12 is formed in an elongated box shape, and the antenna substrate 10 is formed by screws 13 or the like on a central flat portion 12a protruding from a thin plate-like flange portion 12b provided at both ends. It is fixed. In this antenna spacer 12, the antenna element 11 is disposed with the bottom surfaces of the flange portions 12b at both ends serving as attachment surfaces to the vehicle body as attachment surfaces to the vehicle body, and the distance A from the attachment surface of the vehicle body metal to the antenna element 11 is A = It is set to be λ / 4.

  That is, the antenna spacer 12 uses a vehicle body frame made of a metal material as a wave reflector (reflector), and sets the distance A between the antenna element 11 and the vehicle body frame to 1/4 of the wavelength λ of the center frequency of the antenna band. Used to do. By arranging the antenna element 11 via the antenna spacer 12, radio waves can be efficiently transmitted and received from the antenna unit 20.

  Further, when the antenna unit 20 is expected to be disturbed by clutter (random scattering) from the ground, as shown in FIG. 6, a reflector for preventing ground clutter is provided below the antenna unit 20. A unit 21 is disposed. The reflector unit 21 includes a flat reflector 22 and a reflector spacer 23 for mounting on the vehicle body.

  The reflector 22 is formed in a rectangular shape with a conductive material that can prevent the spread and arrival of radio waves in the ground direction, for example, a metal plate such as aluminum. The reflector spacer 23 is formed in a triangular plate shape from a non-conductive material such as a resin material. The reflector spacers 23 are fixed to both ends on the short side of the reflector 22 and attached to the lower part of the antenna unit 20.

  Specifically, as shown in FIG. 7, the reflector unit 21 abuts the long side of the reflector 22 on the long side of the vehicle body mounting surface of the antenna spacer 12 so that the planar portion of the reflector 22 faces the antenna element 11. In this state, the reflector spacer 23 is attached in contact with the metal body frame FL. At this time, as described above, the distance A between the antenna element 11 and the vehicle body frame FL is A = λ / 4 at which the radio wave transmission / reception efficiency is highest. Similarly, the distance B between the antenna element 11 and the planar portion of the reflector 22 is set to B = λ / 4 that can most effectively prevent ground clutter.

  In the present embodiment, the antenna spacer 12 and the reflector spacer 23 are fixed to the vehicle body frame using the double-sided adhesive tape 15.

  Further, when there is a vehicle body metal structure FT that protrudes outward from the vehicle body frame FL that is the mounting surface of the antenna spacer 12, the vehicle body metal structure FT is used as a radio wave reflector (reflector). The antenna unit 20 is installed below the structure FT. Also in this case, the distance C between the lower end of the vehicle body metal structure FT and the center position of the antenna unit 20 is set to be C = λ / 4.

  In particular, the antenna 2 disposed at the lower part of the door on the side of the vehicle body is installed at a position relatively close to the ground surface. Therefore, by setting the distances A, B, and C between the antenna 2 (the antenna unit 20 and the reflector unit 21) and the vehicle body to A = B = C = λ / 4, it is possible to efficiently transmit radio waves while preventing ground clutter. You can send and receive.

  Specifically, as shown in FIG. 8, the antenna unit 20 and the reflector unit 21 are attached to the left and right side sills 106 constituting the metal frame at the lower part of the vehicle body. The antenna unit 20 and the reflector unit 21 attached to the side sill 106 are stored in a side sill spoiler 107 attached to the side sill 106. The side sill spoiler 107 is formed from a member having radio wave transparency such as a resin material.

  At this time, the distance A between the side surface of the side sill 106 and the antenna element 11, the distance B between the antenna element 11 and the flat portion of the reflector 22, and the distance between the lower end of the door 103 (104) and the center position of the antenna unit 20. C is set so that all of them are within a permissible range of λ / 12 to 5λ / 12 with λ / 4 as a representative value (center value) in consideration of the dielectric constant of each part and the mounting accuracy. That is, A, B, and C are all in the range of λ / 4 ± 5λ / 12. As a result, both the performance of the antenna element and the degree of freedom of installation can be achieved. Furthermore, when it is desired to ensure the performance of the antenna element, it may be within the range of λ / 4 ± λ / 12.

  For example, if the center frequency of the antenna band is 3 GHz, the distances A, B, and C are representative values of A = B = C = λ / 4 = 2.5 cm. At this time, if the lateral distance between the lateral side surface of the side sill 106 and the lower end of the door 103 (104) is Y, Y = 1.8 cm. Therefore, although the antenna 2 may protrude slightly laterally from the lower end of the door 103 (104), it is a value that can be sufficiently accommodated in the side sill spoiler 107, and there is no particular inconvenience. The distance H between the center position of the antenna unit 20 and the ground G is, for example, H = 23 cm (15 to 40 cm).

  By arranging the antenna unit 20 and the reflector unit 21 in the above positional relationship, the antenna beam can be effectively directed toward the target. That is, as shown in FIG. 9, with only the antenna unit 20, the antenna beam BM is directed in the direction of the ground G and is obstructed from the ground. On the other hand, by arranging the reflector unit 21 below the antenna unit 20, as shown in FIG. 10, the antenna beam BM can be separated from the ground G, and the ground clutter can be suppressed and the target can be effectively directed. it can.

  Furthermore, the lateral distance L between the transmitting antenna 2a and the receiving antenna 2b is also set to be equal to or greater than a preset distance. That is, as shown in FIG. 9, the transmission beam range of the transmission antenna 2a and the reception beam range of the reception antenna 2b partially overlap, but the other antenna is not positioned within the beam range of one antenna. An interval L is set. For example, when the center frequency of the antenna band is 3 GHz, L = 18 cm or more. As a result, radio waves that directly enter the receiving antenna 2b from the transmitting antenna 2a can be suppressed.

  As described above, in the radar apparatus 1 according to the present embodiment, the antenna is disposed so that the distance between the antenna element 11 and the vehicle body metal frame is ¼ of the wavelength λ of the center frequency of the antenna band. Further, a reflector 22 made of a conductive material such as a metal material is disposed at a distance λ / 4 at a position facing the antenna element 11 in the ground direction. Further, the distance between the transmitting antenna and the receiving antenna is arranged such that the other antenna does not enter the beam pattern of one antenna.

  As a result, the antenna is housed in a space inside the resin parts etc. of the exterior of the vehicle body, making it more compact, preventing the spread and arrival of radio waves in the direction of the earth, suppressing clutter, and unnecessary between the transmitting and receiving antennas Diffraction can be prevented. As a result, the antenna beam can be efficiently narrowed in the direction of the target with an inexpensive configuration, which can contribute to the improvement of ranging accuracy as the radar apparatus.

DESCRIPTION OF SYMBOLS 1 Radar apparatus 2 Antenna 11 Antenna element 22 Reflector 100 Car 106 Side sill λ Wavelength of center frequency of antenna band

Claims (4)

A vehicle radar device that is mounted on a vehicle and detects an object existing around the vehicle by transmitting and receiving radar waves,
It has an antenna attached to the body frame and a reflector attached to the lower part of this antenna to reflect radio waves,
Arrange the distance between the antenna element of the antenna and the body frame and the distance between the antenna element and the reflector to be within a predetermined range centered on 1/4 of the wavelength of the center frequency of the antenna band. A vehicular radar device characterized by the above.   The vehicular radar apparatus according to claim 1, wherein the antenna and the reflector are attached to a side sill of a vehicle body side portion.   3. The antenna according to claim 1, wherein the antenna is arranged as a pair of a transmitting antenna and a receiving antenna, and an interval between the antennas is set such that the other antenna does not enter the beam pattern of one antenna. Vehicle radar system.   4. The predetermined range is within a range of ± 5/12 of the wavelength of the center frequency of the antenna band centering on a quarter of the wavelength of the center frequency of the antenna band. The vehicle radar device according to claim 1.

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