JP2017142074A - Millimeter wave receiving structure - Google Patents

Abstract

Provided is a millimeter wave receiving structure in which detection accuracy is hardly lowered depending on a direction of a reflected wave. In a millimeter wave receiving structure, a millimeter wave radar device transmits a transmission wave and receives a reflected wave obtained by reflecting the transmission wave on an object. The cover 12 transmits the reflected wave of the millimeter wave radar device. The plurality of receiving antennas 20 of the millimeter wave radar apparatus are arranged at equal intervals from a predetermined center position C. The spherical portion 12a of the cover 12 has a spherical shape with the center position C as the center. The receiving antenna 20 receives the reflected wave that has passed through the spherical portion. [Selection] Figure 4

Description

  The present invention relates to a millimeter wave receiving structure including a millimeter wave radar device for detecting an object around a vehicle.

  Patent Document 1 discloses a millimeter wave radar device provided in a vehicle and a radar device cover disposed away from the millimeter wave radar device. The radar apparatus cover has irregularities formed by bending a dielectric plate, and the wall along the cover surface is different from the thickness of the wall perpendicular to the cover surface. This suppresses a phase shift between the millimeter wave transmitted through the wall along the cover surface and the millimeter wave transmitted through the wall perpendicular to the cover surface.

  Patent Document 2 discloses a radar device for recognizing a target existing around a vehicle. The radar apparatus of Patent Document 2 includes a radar unit that transmits and receives radar waves, and a radome that protects a circuit board of the radar unit. This radome is formed of a transmission material that transmits a radar wave with low loss, and is set to a thickness that is a half value of the wavelength of the radar wave with a portion located in the beam direction of the radar unit as a front part. .

JP 2010-230661 A JP 2014-020846 A

  By the way, in recent millimeter wave radar devices, the detectable angular width is widened, and reflected waves greatly inclined with respect to the front direction are received through the cover or radome. However, according to the techniques of Patent Documents 1 and 2, as the reflected wave that passes through the cover or radome is tilted with respect to the front direction, the phase shift increases and the detection accuracy may decrease.

  The present invention has been made in view of such circumstances, and provides a millimeter wave receiving structure in which the detection accuracy is not easily lowered by the direction of the reflected wave.

  In order to solve the above-described problems, a millimeter wave receiving structure according to an aspect of the present invention includes a millimeter wave radar device that transmits a transmission wave and receives a reflected wave reflected from an object, and a millimeter wave radar device. And a cover that transmits the reflected wave. The millimeter wave radar apparatus has a plurality of receiving antennas arranged at equal intervals from a predetermined center position. The cover has a spherical portion having a spherical shape with the center position as the center. The receiving antenna receives the reflected wave that has passed through the spherical portion.

  According to this aspect, the reflected waves received by the plurality of receiving antennas can have the same path length through the spherical portion regardless of the direction. Thereby, in the reflected waves received by the plurality of receiving antennas, the amount of change in phase when passing through the cover can be made equal, and a decrease in detection accuracy due to a phase shift can be suppressed.

  According to the present invention, it is possible to provide a millimeter wave receiving structure in which the detection accuracy is not easily lowered depending on the direction of the reflected wave.

It is a figure for demonstrating the millimeter wave receiving structure of an Example. It is a figure explaining operation | movement of a millimeter wave radar apparatus. It is a figure explaining operation | movement of the millimeter wave radar apparatus received through a cover. It is a figure for demonstrating the position of the cover of an Example, and a receiving antenna. It is a figure for demonstrating the spherical part of the cover of a modification.

  FIG. 1 is a diagram for explaining a millimeter wave receiving structure 1 according to an embodiment. The millimeter wave receiving structure 1 includes a millimeter wave radar device 10 and a cover 12. The millimeter wave radar device 10 is fixed to the vehicle body, outputs a transmission wave toward the front of the vehicle, and receives a reflected wave reflected by an object. The millimeter wave radar apparatus 10 receives reflected waves with a plurality of receiving antennas using an electronic scanning method. The transmission wave of the millimeter wave radar device 10 is a continuous wave in the millimeter wave band that is frequency-modulated along the time axis.

  The detection result of the millimeter wave radar device 10 is sent to a control means (not shown) to detect an object around the vehicle. The detection result of the millimeter wave radar device 10 is, for example, a pre-crash safety system that detects the possibility of a rear-end collision with a preceding vehicle and assists deceleration, or an adaptive that maintains the distance between the preceding vehicle and the host vehicle at an appropriate interval. Used for cruise control.

  The cover 12 is fixed to a front grill 14 provided at the front end of the vehicle. The millimeter wave radar device 10 may also be fixed to the front grille 14. The cover 12 may be a millimeter wave transmitting emblem provided at the center of the front end of the vehicle. The millimeter wave radar apparatus 10 receives the reflected wave that has passed through the cover 12.

  FIG. 2 is a diagram for explaining the operation of the electronic scan type millimeter wave radar apparatus 10. The millimeter wave radar apparatus 10 includes a first reception antenna 20a and a second reception antenna 20b (referred to as “reception antenna 20” if they are not distinguished from each other). The transmitting antenna of the millimeter wave radar device 10 is provided in the vicinity of the receiving antenna 20.

  The transmission wave transmitted from the transmission antenna strikes the object 22 and is reflected, and the reflected wave is received by each of the plurality of reception antennas 20. The first reflected wave 24a is received by the first receiving antenna 20a, and the second reflected wave 24b is received by the second receiving antenna 20b. The first reflected wave 24a and the second reflected wave 24b are substantially parallel.

  Since the first receiving antenna 20a and the second receiving antenna 20b are located apart from each other, a deviation occurs until the first reflected wave 24a and the second reflected wave 24b are received, and the deviation appears as a phase difference L. . Since the phase difference L between the first reflected wave 24a and the second reflected wave 24b changes according to the directions of the first reflected wave 24a and the second reflected wave 24b, the direction of the object 22 can be detected. 2 does not include the action of the cover 12, the action of the cover 12 will be described with reference to a new diagram.

  FIG. 3 is a diagram for explaining the operation of the millimeter wave radar apparatus 10 that receives via the cover 12. The first receiving antenna 20a and the second receiving antenna 20b receive the first reflected wave 24a and the second reflected wave 24b through the cover 12, respectively.

  The first reflected wave 24 a and the second reflected wave 24 b appear as phase shifts due to the shortening of the wavelength while passing through the cover 12. The amount of phase change depends on the path length of the cover 12 through which the reflected wave passes. As shown in FIG. 3, when the path length L2 of the first reflected wave 24a is set to be relatively short and the path length L1 of the second reflected wave 24b is set to be relatively long, the cover 12 through which the reflected wave passes. The difference in path length appears as a phase shift that becomes a detection error.

  Therefore, the cover 12 of the embodiment is configured so that the path lengths of the reflected waves received by the plurality of receiving antennas 20 are equal, thereby suppressing a decrease in detection accuracy.

  FIG. 4 is a diagram for explaining the positions of the cover 12 and the receiving antenna 20 according to the embodiment. As shown in FIG. 4A, the first receiving antenna 20a and the second receiving antenna 20b are provided in the mounting portion 10a of the millimeter wave radar device 10 and are arranged on the same plane.

  The first receiving antenna 20a and the second receiving antenna 20b are separated from the predetermined center position C by the same distance D. That is, the plurality of receiving antennas 20 are located at regular intervals from the center position C.

  The cover 12 has a spherical surface portion 12a formed in a spherical shape, and is arranged around the center position C. In addition to the spherical surface portion 12 a, the cover 12 may integrally include an attachment portion for connecting to the front grill 14 and a grill portion having the same shape as the front grill 14. The spherical surface portion 12a is formed in a substantially hemispherical shape, and is formed of a transmission material that transmits transmission / reception waves of the millimeter wave radar apparatus 10 with low loss.

  The receiving antenna 20 receives a reflected wave that passes through the spherical surface portion 12a. The first reflected wave 24a is received by the first receiving antenna 20a through the spherical portion 12a having the path length L3, and the second reflected wave 24b is received by the second receiving antenna 20b through the spherical portion 12a having the path length L4. Is done. The path length L3 and the path length L4 are equal since the spherical surface portion 12a and the receiving antenna 20 are arranged with the center position C as the center.

  A spherical portion 12 a schematically shown as a sphere in FIG. 4B surrounds the reception antenna 20 and is arranged around the center position C of the reception antenna 20. Here, three first lines 26a, second lines 26b, and third lines 26c that pass through the receiving antenna 20 and the center position C and are parallel to each other are positioned at an equal interval d. An interval L5 where the first line 26a overlaps the spherical surface portion 12a is the same as an interval L6 where the second line 26b overlaps the spherical surface portion 12a.

  In this way, the spherical surface portion 12a of the cover 12 is arranged around the center position C of the plurality of receiving antennas 20, so that the path length of the spherical surface portion 12a in each received reflected wave is independent of the direction of the reflected wave. In the same manner, a decrease in detection accuracy can be suppressed.

  The millimeter wave radar device 10 has a wider detectable angular width by using an electronic scanning method. Further, the reception intensity of the reception antenna 20 decreases as the inclination of the reflected wave with respect to the front direction increases. If the cover has a flat plate shape, the path length passing through the cover becomes longer as the inclination of the reflected wave with respect to the front direction becomes larger, the attenuation of the reflected wave becomes larger, and the reception intensity of the receiving antenna decreases. On the other hand, it is possible to prevent the path length of the reflected wave on the wide angle side from becoming long by transmitting through the spherical surface portion 12a, and it is possible to suppress a decrease in detection accuracy.

  FIG. 5 is a view for explaining the spherical surface portion 112a of the cover 112 according to the modification. The modified spherical portion 112a is formed in a spherical shape having a thickness T, but is different from the spherical portion 12a shown in FIG. 4A in that the center position C is not the center. Note that the center of the spherical portion 112 a is set between the plurality of reception antennas 20 and is located near the center of the plurality of reception antennas 20.

  The reflected wave 28a received by the first receiving antenna 20a passes through the spherical portion 112a having the path length L7, and the reflected wave 28b received by the second receiving antenna 20b passes through the spherical portion 112a having the path length L8. Since the spherical surface portion 112a is not centered on the center position C, the difference between the path length L7 and the path length L8 changes when the direction of the reflected wave changes. The path length L7 and the path length L8 are calculated based on the curvature of the spherical portion 112a, the thickness T of the spherical portion 112a, and the interval D1 of the receiving antenna 20.

In the cover 112 of the modified example, the curvature of the spherical surface portion 112a and the thickness T of the spherical surface portion 112a are set so as to satisfy the following formula 1.
Th> | L8−L7 | max / 2πλ Equation 1
Th is a threshold value of an allowable phase difference, | L8−L7 | max is a maximum value of a path length (phase) difference, and λ is a wavelength of a transmission / reception wave of the millimeter wave radar device 10.

  In this way, by setting the curvature of the spherical surface portion 112a and the thickness of the spherical surface portion 112a so that the maximum phase difference between the path length L7 and the path length L8 is equal to or less than a predetermined allowable threshold value so as to satisfy Expression 1. The detection error of the millimeter wave radar device 10 can be kept within a desired range.

  In the above, this invention was demonstrated based on each embodiment. It is to be understood by those skilled in the art that these embodiments are exemplifications, and various modifications can be made to each component and process combination, and such modifications are also within the scope of the present invention. Such modifications will be described below.

  In the embodiment, the aspect in which the object is provided in front of the millimeter wave radar device 10 and detects the object in front of the vehicle is shown, but the present invention is not limited to this aspect. For example, the millimeter wave radar device 10 is provided respectively in front of and behind the vehicle, and outputs a transmission wave to the front and rear of the vehicle to receive the reflected wave reflected.

  In the embodiment, an aspect in which the number of receiving antennas 20 of the millimeter wave radar apparatus 10 is two is shown, but the present invention is not limited to this aspect, and may be three or more. In any case, the receiving antennas 20 are arranged at equal intervals from the center position C.

  DESCRIPTION OF SYMBOLS 1 Millimeter wave receiving structure, 10 Millimeter wave radar apparatus, 10a Mounting part, 12 Cover, 12a Spherical surface part, 14 Front grille, 20 Receiving antenna, 20a 1st receiving antenna, 20b 2nd receiving antenna, 22 Object, 24a 1st Reflected wave, 24b Second reflected wave.

Claims (1)

A millimeter wave radar device for transmitting a transmission wave and receiving a reflected wave reflected by the object,
A cover that transmits the reflected wave of the millimeter wave radar device,
The millimeter wave radar device has a plurality of receiving antennas arranged at equal intervals from a predetermined center position,
The cover has a spherical portion having a spherical shape centered on the center position,
The millimeter wave receiving structure according to claim 1, wherein the receiving antenna receives a reflected wave transmitted through the spherical portion.

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