JP2007074662A - Millimeter wave radar system - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a millimeter wave radar system which improves detection precision, is made thin and lightweight and improves weather resistance not only by cutting off unwanted radio waves transmitted/received toward an antenna but also by shielding from unwanted radio waves generated from a control device or the like. <P>SOLUTION: The millimeter wave radar system 1 comprises an antenna 12 for transmitting/receiving radio waves, a control circuit 20 for controlling the radio waves, a housing 30 for housing the antenna 12 and the control circuit 20, and a radome 15 covering the antenna 12. The millimeter wave radar system 1 comprises a shielding member 40 for shielding radio waves between the antenna 12 and the control circuit 20. <P>COPYRIGHT: (C)2007,JPO&INPIT

Description

  The present invention is a millimeter wave radar device that is attached to the front surface of a vehicle and detects a relative distance, a relative speed, etc. of a front object in order to safely control driving of an automobile, and more particularly, a radio wave received by the device. The present invention relates to a millimeter-wave radar apparatus that can reduce noise and reduce the size of the apparatus.

  In recent years, millimeter wave radar devices have been used for the purpose of automatic driving of vehicles and collision prevention. As shown in FIGS. 5 and 6, the millimeter wave radar device 50 is attached to the front surface of the host vehicle 70, and includes a high frequency module 11 in which an antenna 12 that transmits and receives radio waves is incorporated, and a control circuit 20 that controls the radio waves. And a housing 30 that houses the antenna 12 and the control circuit 20, and a radome 15 that covers transmission and reception of radio waves from the antenna 12. The antenna 12 is disposed on the inner surface of the housing in the vicinity of the opening 30b provided in the housing 30, and the radome 15 is formed so as to protrude from the housing 30 so as to cover the opening 30b. .

  As shown in FIGS. 5 and 6, the millimeter wave radar device 50 configured as described above transmits a radio wave serving as a transmission main beam a <b> 1 from the antenna 12 in front of the vehicle, and a part of the transmission main beam a <b> 1 is The light is reflected by the vehicle 80 ahead and received by the antenna 12 as a reception main beam a2. Then, the millimeter wave radar device 50 detects a relative distance, a relative speed, and the like between the host vehicle 70 and the vehicle 80 traveling ahead based on the received main beam a2.

  On the other hand, a part of the transmission main beam a1 is reflected by the vehicle 80 ahead and further reflected by the road surface 90 and received by the antenna 12 as the reception side lobe b2. Further, the transmission side lobe b1 transmitted from the antenna 12 is reflected by members such as the bumper 51 and the front grill 52, and is received by the antenna 12 as the reception side lobe b2. Such a reception side lobe b2 becomes noise with respect to the reception main beam a2, and decreases the detection accuracy of the apparatus. In particular, when the host vehicle is traveling, the reception side lobe b2 tends to increase, and the detection accuracy of the apparatus further decreases as the side lobe b2 increases.

  In view of such a problem, a millimeter-wave planar antenna has been proposed in which a metal plate or absorber that protrudes from the surface of the transmitting / receiving antenna is attached around the transmitting / receiving antenna surface in the antenna unit (see Patent Document 1).

  A transmitting / receiving antenna; a casing for housing the transmitting / receiving antenna; and a radome for protecting the transmitting / receiving antenna; A millimeter wave radar provided so as to protrude downward is also proposed (see Patent Document 2).

Further, in a radio wave receiving apparatus including an antenna that receives radio waves and a radome disposed in front of the antenna, the supply of radio waves incident from outside a predetermined angle range with respect to the front of the antenna is restricted. In order to do so, a radio wave receiving apparatus in which a radio wave absorber is arranged in a radome has also been proposed (see Patent Document 3).
JP-A-10-126146 JP 2000-201557 A JP 2000-091839 A

  However, such a device is intended to improve the detection accuracy by reducing the side lobes transmitted and received by the antenna by providing a wave absorber or the like on the wall surface of the radome protruding from the housing. When used, a radio wave having a frequency of about several hundreds KHz is generated as noise c as shown in FIG. 6 from the control circuit. This noise c propagates to the high-frequency module of the apparatus, which increases the noise level of the detected radio wave of the main beam and may reduce the detection accuracy.

  Furthermore, the device as described in Patent Document 1 has a structure in which a metal plate or an absorber attached around a transmission / reception antenna is separated from a radome, making the structure of the antenna unit complicated and the manufacturing process complicated. It will be something. Also, since the metal plate or absorber itself must have a certain level of strength, the thickness of the metal plate or absorber must be increased, and as the thickness increases, the device Will increase in weight. Furthermore, since these metal plates or absorbers are exposed to wind and rain, there is a possibility that problems arise in weather resistance.

  Moreover, since the apparatus as described in patent document 2 has made the shielding member protrude in the front lower part of an antenna unit, when mounting an apparatus in a vehicle, the attachment becomes difficult. Moreover, since the shielding member is exposed as in the device described in Patent Document 1, it is exposed to wind and rain, the metal plate constituting the shielding plate is corroded, and the radio wave absorber is deteriorated. There is a possibility that the shielding characteristic or absorption characteristic of the shielding member may be deteriorated.

  The present invention has been made in view of such problems, and the object of the present invention is not only to block unnecessary radio waves transmitted and received toward the antenna, but also to prevent unnecessary radio waves generated from a control circuit and the like. The object of the invention is to provide a millimeter-wave radar device which improves detection accuracy by shielding and is thin, lightweight and excellent in weather resistance.

  In order to achieve the object, a millimeter wave radar device according to the present invention covers an antenna that transmits and receives radio waves, a control circuit that controls the radio waves, a housing that houses the antenna and the control circuit, and the antenna. A millimeter wave radar device including a radome, wherein the millimeter wave radar device includes a shielding member that shields radio waves between the antenna and the control circuit.

  Since the millimeter wave radar device according to the present invention is provided with a shielding member that shields radio waves between the antenna and the control circuit, unnecessary radio waves such as power source noise from the control circuit can be blocked. Detection accuracy can be improved.

  The millimeter wave radar device according to the present invention is characterized in that the shielding member extends around the antenna along the transmission / reception direction of the radio wave. By providing such a shielding member, the millimeter wave radar apparatus according to the present invention can reduce unnecessary radio waves that become side lobes from being transmitted to and received from the antenna.

  The millimeter wave radar device according to the present invention is characterized in that a thickness of the extended shielding member in the transmission / reception direction is set to a thickness that secures a detection range of the antenna, and the shielding member Is formed in a cylindrical shape, and when the detection angle of the antenna is θ and the distance from the center of the antenna detection angle to the inner wall of the cylindrical shielding member is L, the transmission / reception of the shielding member is The thickness T in the direction is

の関係を満たすものであることを特徴としている。

It is characterized by satisfying this relationship.

  The millimeter-wave radar device according to the present invention transmits the necessary radio wave as a main beam out of the radio waves transmitted and received from the antenna, and is incident from the outside, by setting the shielding member to the optimum thickness in this way. Since the shielding member shields unnecessary radio waves, it is possible to reduce the noise reception of the antenna and improve the detection accuracy of the apparatus.

  In the millimeter wave radar device according to the present invention, the housing has an opening on the housing surface in the radio wave transmission / reception direction, and the shielding member extends to the opening along the radio wave transmission / reception direction. It is characterized by having.

  The millimeter wave radar apparatus according to the present invention can protect the antenna by reducing not only the antenna but also the shielding member in the housing, thereby reducing the thickness of the apparatus in the radio wave transmission / reception direction. The apparatus can be made thinner and lighter. In addition, since the shielding member is not exposed to wind and rain, the weather resistance of the apparatus is improved.

  Furthermore, the millimeter wave radar device according to the present invention is characterized in that the control circuit is arranged in parallel with the antenna on a plane perpendicular to the radio wave transmission / reception direction of the antenna. The millimeter wave radar apparatus according to the present invention can simplify the apparatus configuration and reduce the weight of the apparatus by arranging the antenna and the control circuit in parallel in the housing.

  In the millimeter wave radar device according to the present invention, the shielding member includes a radio wave absorber. In the millimeter wave radar apparatus as in the present invention, the radio wave absorber can absorb unnecessary radio waves that become noise.

  In the millimeter wave radar device according to the present invention, the radio wave absorber is formed by laminating a conductor layer on either a dielectric loss layer or a magnetic loss layer having a dielectric loss larger than that of the radome. . The millimeter wave radar device according to the present invention is provided with a layer having a dielectric loss larger than that of the radome, so that necessary radio waves can pass through the radome and unnecessary radio waves can be absorbed in the dielectric loss layer. Even in the case of the magnetic loss layer of the radio wave absorber, unnecessary radio waves incident on the shielding member can be absorbed. Furthermore, the dielectric layer can absorb unnecessary radio waves that could not be absorbed by the dielectric loss layer or the magnetic loss layer.

  In the millimeter wave radar device according to the present invention, the dielectric loss layer is made of a carbon material selected from at least one of carbon nanotubes, carbon microcoils, sungite carbon, carbon black, expanded graphite, and carbon fibers. Features. Furthermore, the millimeter wave radar device according to the present invention is characterized in that the magnetic loss layer is made of hexagonal ferrite. The millimeter wave radar apparatus according to the present invention can have excellent electromagnetic wave absorption characteristics by using such a material.

  In another aspect, the dielectric loss layer or the magnetic loss layer contains a substance having a higher electrical resistivity than the carbon material or the hexagonal ferrite, and the high electrical resistance The substance having a rate is an insulating polymer material or an insulating inorganic material. The millimeter wave radar apparatus according to the present invention can further improve the radio wave absorption characteristics when such a material is used.

  According to the present invention, by providing a shielding member between the control device and the antenna, unnecessary radio waves generated from the control device or the like can be shielded, and detection accuracy can be improved. Furthermore, by providing such a shielding member in the housing, it is possible to obtain a thin, lightweight, and weather resistant device.

Hereinafter, embodiments of a millimeter wave radar device according to the present invention will be described with reference to the drawings.
FIG. 1 is an overall configuration diagram of a millimeter wave radar device according to the present embodiment, (a) is a sectional view of the device, and (b) is a diagram of the device viewed from the front. FIG. 2 is a diagram for explaining the optimum thickness of the shielding member of the millimeter wave radar apparatus shown in FIG. The components having the same functions as those shown in FIG. 5 such as the antenna and the control circuit constituting the millimeter wave radar apparatus are denoted by the same reference numerals, and detailed description thereof is omitted.

  As shown in FIG. 1, the millimeter wave radar device 1 according to the present embodiment includes a high frequency module 11 in which an antenna 12 for transmitting and receiving radio waves is incorporated, a control circuit 20 for controlling the radio waves, the high frequency module 11 and A housing 30 that houses the control circuit 20 and a radome 15 that covers the antenna 12 are mainly provided.

  The housing 30 includes a base plate portion 31, a housing portion 32 extending from the base plate portion 31 so as to form an internal space 30 a in the housing, and a lid portion that covers the housing portion 32 so as to face the base plate portion 31. 33. Further, an opening 30b communicating with the internal space 30a is formed on the upper surface (housing surface) 30c of the lid 33 in the radio wave transmission / reception direction, and a radome 15 (to be described later) is formed so as to cover the opening 30b. Has been placed. As described above, by providing the lid portion 33 and the radome 15, the high-frequency module 11 including the control circuit 20 and the antenna 12 can be protected from stone splash and rain.

  And the control circuit 20 and the high frequency module 11 are arrange | positioned in parallel on the same surface perpendicular | vertical with respect to the transmission / reception direction of the electromagnetic wave of the antenna above the baseplate part 31 of the internal space 30a of the housing 30, A cylindrical shielding member 40 extends from the periphery of the antenna 12 of the high-frequency module 11 to the opening 30b of the housing 30 along the transmission / reception direction of the radio wave so that the radio wave of the antenna 12 can be transmitted / received. Yes. By arranging the shielding member 40 formed in such a cylindrical shape, the shielding member 40 shields between the antenna 12 and the control circuit 20.

  As shown in FIG. 2, when the detection angle of the antenna 12 is θ, and the distance from the center of the antenna detection angle θ to the inner wall of the cylindrical shielding member 40 is L, the shielding member 40 The thickness T in the transmission / reception direction is:

の関係を満たすようになっている。

To meet the relationship.

  In this way, the thickness of the housing portion 32 of the housing 30 is determined in accordance with the thickness T of the shielding member 40, and the antenna 12 is placed inside the housing by the thickness of the shielding member 40 without impairing radio wave absorption characteristics. Since it can be submerged, the millimeter wave radar device 1 can be reduced in thickness and size.

  The shielding member 40 is made of a radio wave absorber for absorbing radio waves, and this radio wave absorber has either a dielectric loss layer or a magnetic loss layer having a dielectric loss larger than that of the radome 15. Furthermore, a conductor layer 42 is laminated on the outer side surface in order to improve radio wave absorption characteristics.

  When the dielectric loss layer is provided, the dielectric loss layer is made of a carbon material selected from at least one of carbon nanotubes, carbon microcoils, sungite carbon, carbon black, expanded graphite, and carbon fibers. Preferably, it is configured. Further, when a magnetic loss layer is provided, the magnetic loss layer is preferably composed of hexagonal ferrite. As a more preferred embodiment, the dielectric loss layer or the magnetic loss layer contains a substance having a higher electrical resistivity than the carbon material or the hexagonal ferrite, and the substance having the higher electrical resistivity is: It is desirable to be selected from either an insulating polymer material or an insulating inorganic material. Further, the material having a high electrical resistivity may be the same material as that of the radome 15. In this case, the radome and the shielding member can be integrally formed, which is advantageous in manufacturing.

  With such an apparatus configuration, as shown in FIG. 3, the transmission main beam a1 transmitted from the antenna reaches the front vehicle 80 via the radome 15, and the reception main beam a2 reflected from the object is The distance received by the antenna 12 and the distance to the object can be detected.

  Further, the shielding member 40 can not only shield the transmission side lobe b1 transmitted from the antenna 12 and the reception side lobe b2 reflecting the road surface 90, but also between the antenna 12 and the control circuit 20. Since the blocking member 40 is arranged, unnecessary radio waves such as power source noise from the control circuit 20 can be blocked, and the detection accuracy of the radar can be improved.

  FIG. 4 is a diagram for explaining the result of evaluating the characteristics of the clutter noise with the millimeter wave radar according to the present embodiment attached to the vehicle. The normalized frequency on the horizontal axis indicates the Doppler based on the relative velocity of the detected object. The frequency is normalized by the Doppler frequency corresponding to the vehicle speed, and the vertical axis indicates the received signal intensity of the millimeter wave radar device 1.

As shown in FIG. 6, when the vehicle on which the radar is mounted is stationary, the relative speed with respect to the road surface is not generated, so that the received signal strength is low. However, when the vehicle travels at a speed V ₀ , a radio wave of a relative speed component (V ₀ cosφ) with respect to the road surface is generated, and when there is no shielding member 40, a radio signal (side lobe) of the relative speed component from the road surface is generated. ) Is received as noise. However, as shown in FIG. 4, the millimeter wave radar device 1 according to the present embodiment is provided with the shielding member 40, so that the relative velocity component V ₀ cosφ = 0V _{0 described} above is provided. Unnecessary radio wave signals up to ~ 0.45V ₀ (45% of the speed of the vehicle) can be reliably reduced, so the detection accuracy during this period has not deteriorated, and is equivalent to that at rest. And the detection accuracy of the entire apparatus is improved.

  Although several embodiments of the millimeter wave radar device according to the present invention have been described in detail above, the present invention is not limited to the above-described embodiments, and the spirit of the present invention described in the claims. Various design changes can be made without departing from the above.

  For example, in the present invention, the shielding member is arranged in the housing, but separately from this, a shielding plate for shielding radio waves may be further provided in the vertical direction of the housing, and by providing such a plate, Road clutter during vehicle travel can be further reduced.

BRIEF DESCRIPTION OF THE DRAWINGS It is a whole block diagram of the millimeter wave radar apparatus concerning this embodiment, (a) is apparatus sectional drawing, (b) is the figure which looked at the apparatus from the front. The figure for demonstrating the optimal thickness of the shielding member of the millimeter wave radar apparatus shown in FIG. The figure for demonstrating transmission / reception of the electromagnetic wave of the millimeter wave radar apparatus shown in FIG. The figure for demonstrating the result of having attached the millimeter wave radar apparatus which concerns on this embodiment to the actual vehicle, and performing the clutter noise characteristic evaluation. The figure for demonstrating the electromagnetic wave transmitted / received in the vehicle using the conventional millimeter wave radar apparatus. The whole block diagram of the conventional millimeter wave radar apparatus.

Explanation of symbols

  DESCRIPTION OF SYMBOLS 11 ... High frequency module, 12 ... Antenna, 15 ... Radome, 20 ... Control circuit, 30 ... Housing, 30a ... Internal space, 30b ... Opening part, 30c ... Housing surface, 31 ... Base plate part, 32 ... Housing part, 33 ... Cover body part, 40 ... shielding member, 51 ... bumper, 52 ... front grille, 80 ... vehicle, 90 ... road surface, a1 ... transmission main beam, a2 ... reception main beam, b1 transmission side lobe, b2 ... reception side lobe, c …noise

Claims (12)

A millimeter-wave radar device comprising: an antenna that transmits and receives radio waves; a control circuit that controls the radio waves; a housing that houses the antenna and the control circuit; and a radome that covers the antenna,
The millimeter wave radar device includes a shielding member that shields radio waves between the antenna and the control circuit.   The millimeter wave radar device according to claim 1, wherein the shielding member extends around the antenna along a transmission / reception direction of the radio wave.   3. The millimeter wave radar device according to claim 1, wherein a thickness of the extending shielding member in the transmission / reception direction is set to a thickness that secures a detection range of the antenna. 4. The shielding member is formed in a cylindrical shape, and when the detection angle of the antenna is θ and the distance from the center of the antenna detection angle to the inner wall of the cylindrical shielding member is L, the shielding member The thickness T of

The millimeter wave radar device according to claim 3, wherein the relationship is satisfied.   The said housing has an opening part in the housing surface of the said radio wave transmission / reception direction, The said shielding member is extended to the said opening part along the said radio wave transmission / reception direction. 5. The millimeter wave radar device according to any one of items 1 to 4.   The millimeter wave radar according to any one of claims 1 to 5, wherein the control circuit is arranged in parallel with the antenna on a plane perpendicular to the radio wave transmission / reception direction of the antenna. apparatus.   The millimeter wave radar device according to any one of claims 1 to 6, wherein the shielding member includes a radio wave absorber.   8. The millimeter wave radar device according to claim 7, wherein the radio wave absorber is formed by laminating a conductor layer on either a dielectric loss layer or a magnetic loss layer having a dielectric loss larger than that of the radome. .   The millimeter dielectric according to claim 8, wherein the dielectric loss layer is made of a carbon material selected from at least one of carbon nanotube, carbon microcoil, sungite carbon, carbon black, expanded graphite, and carbon fiber. Wave radar device.   9. The millimeter wave radar device according to claim 8, wherein the magnetic loss layer is made of hexagonal ferrite.   The millimeter wave radar device according to claim 10, wherein the dielectric loss layer or the magnetic loss layer contains a substance having a higher electrical resistivity than the carbon material or the hexagonal ferrite. 12. The millimeter wave radar device according to claim 11, wherein the substance having a high electrical resistivity is an insulating polymer material or an insulating inorganic material.

Images