JPH08334557A - Radar apparatus carried on vehicle - Google Patents

Abstract

PURPOSE: To provide a radar apparatus carried on a vehicle, by which the direction of an obstacle at a long distance can be detected with good accuracy and by which an obstacle at a short distance can be detected surely. CONSTITUTION: The radar apparatus carried on a vehicle is provided with an antenna element group 2 which is composed of a plurality of antenna elements 2a to 2q and in which directing directions of the adjacent antenna elements are arranged and installed so that they are different from each other little by little. Switches 3a to 3q are interposed and installed between the respective antenna elements 2a to 2q and a transmission-reception part 4. In a long- distance detection, the plurality of antenna elements are used so as to perform a transmitting-receiving operation in which the beam width of an antenna is narrowed to enhance their bearing resolution. In a short-distance detection, the antenna elements whose number is smaller than that in the long-distance detection are used so as to perform a transmitting-receiving operation in which the beam width of the antenna has been expanded. Thereby, the omission of the detection of an obstacle is eliminated.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a vehicle-mounted radar device equipped with a plurality of antenna elements, and more particularly, by changing the antenna element or antenna element group used for transmission / reception to change the beam direction and beam width of the antenna. The present invention relates to a vehicle-mounted radar device that detects the direction and distance of an obstacle.

[0002]

2. Description of the Related Art An on-vehicle radar system, which uses an array antenna composed of a plurality of antenna elements and is capable of varying the total beam width of the antennas by connecting and disconnecting the antenna elements, is disclosed in Japanese Unexamined Patent Publication No. Hei 2 (1999) -211. -2871
No. 81 is proposed.

A vehicle-mounted radar that uses a phased array antenna composed of a plurality of antenna elements and a plurality of phase shifters, and switches the beam amount of the phased array antenna in the traveling direction of the vehicle by switching the phase amount of the phase shifter. A system is proposed in Japanese Patent Laid-Open No. 2-287180.

[0004]

[Patent Document 1] Japanese Patent Application Laid-Open No. 2-28718
The vehicle-mounted radar system proposed in Japanese Patent Publication No. 1 can detect an obstacle in an appropriate beam width state by switching the beam width according to the distance to the obstacle. However,
Since the beam direction of the antenna cannot be changed, the direction of the obstacle such as whether the obstacle is on the left side or the right side in front of the vehicle cannot be detected.

Since the vehicle-mounted radar system proposed in Japanese Patent Laid-Open No. 2-287180 can switch the beam direction of the antenna, it is possible to detect the direction of the obstacle, but the beam direction is switched. Requires a phase shifter, which complicates the configuration.

Since the level of the reflected signal from the obstacle at a short distance is large and the level of the reflected signal from the obstacle at a long distance is small, a wide dynamic range is required for the receiver. Further, if there is a large vehicle or the like having a large radio wave reflectance in a short distance, the receiver may have an excessive input and the detection accuracy may deteriorate. Therefore, it is desired to effectively utilize the dynamic range of the receiver so that highly accurate detection can be performed.

The present invention has been made in order to solve such a problem, and by changing the direction of the antenna beam and changing the width of the antenna beam with a simple structure without using a phase shifter or the like, It is an object of the present invention to provide a vehicle-mounted radar device capable of accurately detecting the direction of an obstacle at a distance and surely detecting an obstacle at a short distance.

[0008]

In order to solve the above-mentioned problems, a vehicle-mounted radar device according to the present invention comprises a plurality of antenna elements, and the antenna element groups are arranged such that the directivity directions of adjacent antenna elements are slightly different from each other. And switching the detection direction by selectively switching one or more antenna elements used for transmission and reception among the plurality of antenna elements, and at the time of long-distance detection, a plurality of adjacent antenna elements are used to reduce the beam width of the antenna. It is characterized in that narrow transmission / reception is performed, and during short-distance detection, a smaller number of antenna elements are used than in long-distance detection to perform transmission / reception with a wide beam width of the antenna.

[0009]

When a long distance is detected, by using a plurality of adjacent antenna elements, transmission / reception with a narrow beam width can be performed. By narrowing the beam width, it is possible to detect far distances even if the transmission power is constant. Since each antenna element has a slightly different pointing direction, the detection direction can be changed by switching the antenna elements used for transmission and reception. Therefore, it is possible to determine in which direction the obstacle exists.

In short distance detection, the number of antenna elements used for transmission / reception is set to one or less than in long distance detection, so the beam width of the antenna becomes wider and the power per predetermined azimuth angle becomes smaller. Therefore, the level of the reflected wave from a long distance becomes lower and detection becomes impossible, so that the detection range is limited to a short distance. Since the beam width is wide, there are few detection omissions even if the reflector is small. By switching the antenna element used for transmission and reception and detecting in each direction,
In which direction the obstacle is present can be determined.

Since the antenna gain is increased during long-distance detection, the level of the reflected signal increases. Since the antenna gain is reduced during short-distance detection, even if the object has a large reflection coefficient in the close range, the degree of excessive reception level can be reduced. The antenna gain is increased so that the reception level increases during long-distance detection, and the antenna gain is decreased during short-distance detection so that the reception level does not become excessive. It can detect efficiently from a distance to a long distance.

[0012]

Embodiments of the present invention will be described below with reference to the accompanying drawings. FIG. 1 is a block diagram of a vehicle-mounted radar device according to the present invention. The on-vehicle radar device 1 includes an antenna element group 2 including a plurality of antenna elements 2a to 2q, a beam direction / beam width switching unit 3, a transmitting / receiving unit 4, a control unit 5, a display unit 6, and operation control. And device 7.

The antenna element group 2 includes a plurality of antenna elements 2
a to 2q are arranged at predetermined intervals in the vehicle width direction. Each of the antenna elements 2a to 2q is composed of a patch antenna in which a plurality of rectangular antennas are connected in series.

FIG. 2 is an explanatory view showing the pointing directions of the respective antenna elements. FIG. 2 shows each antenna element 2a to the front side of the vehicle.
2q is an example in which the antenna element 2i located at the center in the vehicle width direction is directed toward the front of the vehicle.
The antenna elements 2a to 2h arranged on the left side of the antenna element 2i with respect to the vehicle traveling direction are arranged on the right side of the antenna element 2i with respect to the vehicle traveling direction by slightly shifting the pointing direction to the left. Each installed antenna element 2j-
2q gradually shifts its pointing direction to the right.

FIG. 3 is a beam pattern diagram of a single antenna element, and FIG. 4 is a combined beam pattern diagram when a plurality of antenna elements are fed in parallel. As shown in FIG. 3, the beam pattern of one antenna element has a wide beam width and a small antenna gain in the pointing direction. When a plurality of adjacent antenna elements (for example, 5 antenna elements of 2k to 21) are used at the same time, their combined beam patterns have a narrow beam width and a large antenna gain in the pointing direction as shown in FIG.

The beam direction / beam width switching means 3 shown in FIG. 1 comprises switches 3a to 3q individually corresponding to the antenna elements 2a to 2q, and a beam control means 3z. The beam control means 3z makes one or a plurality of switches 3a to 3q conductive based on the detection direction / detection distance range command 5a supplied from the control unit 5. For example, when a command to detect a long distance in the direction I shown in FIG. 2 is received, the beam control means 3z causes the antenna element 2i directed in the direction I and adjacent two antenna elements 2g, 2 adjacent to the antenna element 2i.
The switches 3g to 3k are controlled to be conductive so that transmission and reception can be performed using a total of five antenna elements h, 2j, and 2k. As a result, a beam pattern having a narrow beam width is formed as indicated by the symbol PI in FIG. 5, and a long distance up to about 100 meters can be detected. The direction of the beam pattern, that is, the detection direction can be changed by switching the antenna element used for transmission and reception.

For example, when a command for short-distance detection is received in the direction I, the beam control means 3z causes the antenna element 2i corresponding to the required direction and the antenna elements 2h, 2 on both sides thereof.
The switches 2h to 2j are turned on so that transmission and reception can be performed using the three antenna elements of j. Antenna element 2
You may make it transmit and receive only with i. Since the number of antenna elements used for transmission and reception is reduced during short-distance detection,
As shown in FIG. 6, the beam width of the beam pattern pI becomes wider. In this short distance detection mode, for example, a short distance of about 20 meters can be detected. The direction of the beam pattern can be changed by switching the antenna element used for transmission and reception.

As shown in FIG. 1, the transmission / reception unit 4 has an FM-
It has a CW radar system configuration and includes a voltage control type high frequency signal generation circuit 4a, a power distributor 4b, a circulator 4c, a mixer (mixer) 4d, and a sweeping means 4e. The sweeping means 4e outputs a triangular wave or sawtooth-shaped voltage signal based on the sweep command 5b supplied from the controller 5, and causes the voltage control type high frequency signal generating circuit 4a to generate a frequency-modulated high frequency signal. The frequency-modulated high-frequency signal is supplied to the power distributor 4b and the circulator 4
It is supplied to the antenna element 2n through the switch c and the switch 3n which is made conductive, and is radiated as a radio wave.
The reflected wave received by the antenna element 2n is transmitted to the switch 3
n, and is supplied to the mixer 4d via the circulator 4c. The mixer 4d mixes a part of the transmission signal supplied via the power distributor 4b and the reception signal supplied via the circulator 4c, and the beat signal 4 of those signals is mixed.
Output f.

The control unit 5 outputs the detection direction / detection distance range command 5a to specify the antenna element to be used for transmission / reception, and then outputs the sweep command 5b to transmit / receive the FM-CW signal. Beat signal 4f output from 4
Analyze the frequency spectrum of. This is repeated while changing the detection direction and the beam width, and the distance data to the obstacle is obtained for each direction, and the distance data is stored / updated in association with the detection direction.

The control unit 5 generates image information indicating the presence or distance of the obstacle based on the obtained distance data and supplies it to the image display device 6a in the display unit 6 to display the image. In addition, the control unit 5 voice-guides information such as the presence of the obstacle, the direction of the obstacle, and the distance via the voice synthesizer 6b.

Further, the control unit 5 automatically controls the driving of the vehicle through the driving control device 7 based on the surrounding condition of the vehicle obtained by the radar detection, or operates the accelerator pedal to secure the safety or A reaction force can be applied to the steering wheel operation. For example, when the inter-vehicle distance to the preceding vehicle becomes short, a braking command is generated, or when there is an obstacle in front of the vehicle, a reaction force is applied to the steering wheel to the left to operate the steering wheel. You may make it alert a driver by making it heavy. Further, when the cruise operation is set on the highway or the like, the vehicle speed can be automatically adjusted by outputting the throttle command based on not only the distance between the preceding vehicles but also the diagonally forward situation.

The control unit 5 switches the detection direction and the detection distance range in a preset order. However, when an obstacle is detected, the direction of the obstacle may be frequently detected. Further, if it is determined that the vehicle is traveling at a high speed based on the vehicle speed information supplied from a vehicle speed detector (not shown), the ratio of long-distance detection may be increased.
When the route information including the route change based on the direction indicator or the steering wheel operation is supplied, the detection ratio of the direction on the route change side may be increased.

FIG. 7 is a block diagram of another vehicle-mounted radar device according to the present invention. This on-vehicle radar device 11
Is provided with circulators 12a to 12q corresponding to the respective antenna elements 2a to 2q, between the transmission power input terminals of the circulators 12a to 12q and the voltage control type high frequency signal generating circuit 4a, and the circulators 12a. ~ 12q reception output terminal and mixer 4b
A beam direction / beam width switching means 13 is provided between and. The beam direction / beam width switching means 13 includes transmission power amplifiers 14a to 14q and a reception signal amplifier 15a.
.About.15q are provided corresponding to the respective circulators 12a to 12q, and a synthesizing circuit 16 for synthesizing the outputs of the reception signal amplifiers 15a to 15q is provided.

The power amplifiers 14a to 14q for transmission have a structure in which the power amplification function operates only while the operation permission signal 17 is given. Transmission power amplifiers 14a-14
Since a predetermined transmission power is supplied to each antenna element using q, increasing the number of antenna elements used for transmission and reception for long-distance detection will increase the beam gain of the antenna and increase the transmission power. Since it also increases, the detection distance can be increased. In addition, the level of the reflected signal also increases. When the number of antenna elements used for short-distance detection is reduced, the beam gain of the antenna is reduced, the power to be transmitted is also reduced, and the level of the reflected signal is also reduced, so that only short-distance detection is possible. Even if the object has a large reflection coefficient at a short distance, the degree of excessive reception level can be reduced. In this way, the antenna gain and the transmission power are increased so that the reception level is increased during the long range detection, and the antenna gain and the transmission power are decreased during the short range detection so that the reception level does not become excessive. Even if it is constant, it can detect efficiently from a short distance to a long distance.

The receiving signal amplifiers 15a to 15q have an amplifying function which operates only while the operation permission signal 17 is supplied,
The amplified output is supplied to the synthesis circuit 16.
The reception signal amplifiers 15a to 15q may have no amplification function and may simply switch between passing and blocking signals.

The control unit 17 selects an antenna element to be used for transmission / reception according to the operation permission signal 17. For example, when transmitting and receiving using only the antenna element 2a, the transmission power amplifier 14a and the reception signal amplifier 15a are controlled to the operating state. After setting the detection direction and the beam width by selecting the antenna element, the control unit 17 causes the sweep command 5
b is output and the FM modulated wave is transmitted. In this embodiment, the FM modulation signal output from the voltage control type high frequency signal generation circuit 4a is passed through the level adjuster 18 to the mixer 4b.
To supply. Attenuation variable type level controller is used.
The level of the FM modulation signal supplied to the mixer 4b may be changed according to the number of antennas used for transmission / reception.

Although the FM-CW type radar device is illustrated in FIGS. 1 and 7, the present invention can be applied to a radar or a pulse type radar in which an amplitude modulated signal is transmitted and a distance is obtained from a phase difference.

[0028]

As described above, the vehicle-mounted radar device according to the present invention is provided with the antenna element group which is composed of a plurality of antenna elements and is arranged so that the directivity directions of the adjacent antenna elements are slightly different from each other. The direction and beam width of the antenna beam can be changed by selectively switching the antenna element to be used for, and at the time of long-distance detection, transmission and reception with narrowed beam width of the antenna are performed for each detection direction by using a plurality of adjacent antenna elements. At the time of short-distance detection, the number of antenna elements used is smaller than that at the time of long-distance detection, and the transmission / reception in which the beam width of the antenna is widened is performed for each detection direction, so that the direction of a long-distance obstacle can be detected accurately. It is possible to reliably detect an obstacle in a short distance.

Since the antenna gain is increased during long-distance detection, the level of the reflected signal increases. Since the antenna gain is reduced during short-distance detection, even if the object has a large reflection coefficient in the close range, the degree of excessive reception level can be reduced. The antenna gain is increased so that the reception level increases during long-distance detection, and the antenna gain is decreased during short-distance detection so that the reception level does not become excessive.Therefore, even if the dynamic range of the receiving system is constant, It can detect efficiently from a distance to a long distance.

Since the direction of each antenna element is slightly shifted and the antenna beam direction and beam width are changed by selecting one or more antenna elements to be used for transmission / reception, a phase shifter or the like is used. The beam direction can be changed without the need. Therefore, the structure of the radar device is simplified.

[Brief description of drawings]

FIG. 1 is a block configuration diagram of a vehicle-mounted radar device according to the present invention.

FIG. 2 is an explanatory diagram showing the direction of orientation of each antenna element.

FIG. 3 is a beam pattern diagram of a single antenna element.

FIG. 4 is a synthetic beam pattern diagram when a plurality of antenna elements are fed in parallel.

FIG. 5 is an explanatory diagram of a detection range and a detection direction during long-distance detection.

FIG. 6 is an explanatory diagram of a detection range and a detection direction at short range detection.

FIG. 7 is a block configuration diagram of another vehicle-mounted radar device according to the present invention.

[Explanation of symbols]

 1, 11 In-vehicle radar device 2 Antenna element groups 2a to 2q Antenna element 3,13 Beam direction / beam width switching means 4 Transmitting / receiving section 5,17 Control section 6 Display section

Claims (1)

[Claims] 1. An antenna element group comprising a plurality of antenna elements and arranged so that the directivity directions of adjacent antenna elements are slightly different from each other, and one or more antenna elements used for transmission and reception among the plurality of antenna elements. In addition to switching the detection direction by selecting and switching, the antenna beam width is narrowed using multiple adjacent antenna elements during long-distance detection, and a smaller number of antenna elements are used during short-distance detection than during long-distance detection. An in-vehicle radar device characterized in that a beam width of an antenna is widened for transmission / reception.