JP3073111B2 - Radar equipment - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a radar device suitably used as an inter-vehicle distance radar of an automobile.

[0002]

2. Description of the Related Art In recent years, automobiles have been equipped with a constant-speed traveling device for controlling the throttle valve opening so that the traveling vehicle speed becomes a predetermined target vehicle speed. In this constant speed traveling device, the inter-vehicle distance control for following the preceding vehicle with a safe inter-vehicle distance between the vehicle and the preceding vehicle when the constant speed traveling cannot be maintained on a relatively congested road or the like is performed. It is becoming.

A radar apparatus for measuring the inter-vehicle distance radiates a transmission signal obtained by frequency-modulating a carrier wave with, for example, a triangular wave from an antenna toward a preceding vehicle which is an object to be detected, and generates a reflected wave due to scattering of the preceding vehicle. The inter-vehicle distance to the preceding vehicle, the relative speed, and the like are detected based on the phase difference between the received signal and a signal obtained by mixing a part of the transmission signal. As an antenna used in such a radar device, for example, a slot array antenna is given. This antenna is mounted by being embedded in a front grill of a vehicle body or the like, so that the antenna length cannot be formed so long that there is a problem that directivity is deteriorated. Therefore, conventionally, the directivity has been improved by changing the depth of the slot formed in the primary radiator of the antenna to change the intensity distribution of the radio wave radiated from the aperture surface of the antenna. I have.

[0004]

In the above-mentioned prior art, in order to improve the directivity, that is, to reduce the beam width of the main lobe, due to the characteristics of the antenna, the side lobes generated symmetrically with respect to the main lobe. The energy is increased and the beam width is increased. For this reason,
Vehicles running in parallel in the next lane are also likely to be affected by unnecessary reflectors such as detection by side lobes. For this reason, it is necessary to identify whether the detected target is in the main lobe or the side lobe.

[0005] It is an object of the present invention to provide a radar apparatus capable of distinguishing whether a detected target is in a main lobe or a side lobe.

[0006]

According to the present invention, there is provided a radar apparatus for measuring a distance to an object to be detected based on a phase difference between a radio wave radiated from the antenna and a reflected wave from the object. It includes a displacement unit that displaces in a direction that intersects with a direction in which radio waves are radiated, and a determination unit that determines whether a level change corresponding to the displacement speed of the antenna has occurred from a received signal of the reflected wave. It is a radar device.

[0007]

According to the present invention, a radar device mounted on a vehicle and used for detecting an inter-vehicle distance radiates a radio wave from an antenna, and reflects a reflected wave from an object to be detected such as a preceding vehicle and a radiated radio wave. The distance to the detected object, the relative speed, and the like are measured based on the phase difference with the target. In the radar apparatus used in this manner, in the present invention, a displacement unit and a determination unit are provided. The displacement means displaces the antenna in a direction intersecting with the radiation direction of the radio wave, for example, in a direction perpendicular to the radiation direction of the main lobe.
The determination means determines whether or not a level change corresponding to the displacement speed of the antenna has occurred in the received signal of the reflected wave.

That is, the reflected wave due to the side lobe generated at a predetermined angle θ from the center line of the main lobe has a level fluctuation corresponding to the Doppler velocity obtained by multiplying the displacement velocity of the antenna by cos θ. Has occurred. Whether or not the detected object is in the main lobe or in the side lobe can be identified based on whether or not this level fluctuation is detected. Therefore, it is possible to accurately detect only the object to be detected ahead such as the preceding vehicle without being affected by an unnecessary reflector such as a vehicle running in the adjacent lane.

[0009]

FIG. 1 shows a radar apparatus 20 according to an embodiment of the present invention.
FIG. 3 is a block diagram for explaining a configuration related thereto. The radar device 20 is provided in association with the constant speed traveling device 21. The control circuit implemented by a microcomputer or the like controls the stepping motor so that the traveling vehicle speed detected by the vehicle speed sensor 7 becomes the target vehicle speed set in response to the operation of the switch 6 or the like. This is a device that adjusts and controls the throttle valve opening degree by a throttle actuator 8 realized by, for example, the above. When the constant-speed traveling device 21 cannot maintain the constant-speed traveling control, for example, when traveling on a relatively congested road, the control circuit 9 determines that the inter-vehicle distance detected by the radar device 20 is a safe inter-vehicle distance corresponding to the traveling vehicle speed. The follow-up running can be performed by controlling the throttle actuator 8 so as to be the distance.

The radar apparatus 20 includes an antenna 4, a detection circuit 5, an arithmetic circuit 1, a drive circuit 2, and a drive mechanism 3. The arithmetic circuit 1 includes a detection circuit 5
For example, a transmission signal in which a carrier wave of 50 GHz is frequency-modulated by a triangular wave is generated, and this transmission signal is radiated from the antenna 4 toward a preceding vehicle as an object to be detected. The reflected wave from the preceding vehicle is received by the antenna 4, and the received signal is input to the detection circuit 5. The detection circuit 5 mixes a part of the transmission signal and the reception signal, and outputs an output corresponding to a phase difference between the two to the arithmetic circuit 1. The arithmetic circuit 1 calculates an inter-vehicle distance to a preceding vehicle, a relative speed, and the like based on the phase difference, and outputs the calculated distance to the control circuit 9 of the constant-speed traveling device 21 for the following traveling.

In the present invention, the radar device 20 is also provided with the antenna 4 in the direction of emission of the transmission signal indicated by the arrow 22, ie, in the front-rear direction of the vehicle body on which the radar device 20 is mounted. A drive mechanism 3 for driving a vertical displacement of the vehicle body in the lateral direction indicated by 23 and a drive circuit 2 for controlling the drive of the drive mechanism 3 are provided. The driving mechanism 3 is realized by, for example, a stepping motor. To the driving mechanism 3, driving power is supplied from the driving circuit 2 in response to a driving output from the arithmetic circuit 1. The output from the drive circuit 2 is also input to the arithmetic circuit 1, whereby the arithmetic circuit 1 can detect the displacement speed and the displacement position of the antenna 4. The arithmetic circuit 1 determines whether the detected object is due to the main lobe or the side lobe from the received signal of the antenna 4 according to the displacement speed, as described later, Is determined as the preceding vehicle, and the detected inter-vehicle distance and relative speed are output to the control circuit 1.

FIG. 2 is a perspective view of the antenna 4. The antennas 4 are arranged in a pair on the left and right sides of the vehicle body, such as in a front grill of an automobile. Also, this antenna 4
Is referred to as a slot array antenna, and generally includes a primary radiator 10 and a secondary radiator 11.
The secondary radiator 11 is formed in a semi-cylindrical shape, and on its axis,
A quadrangular cylindrical primary radiator 10 supported by semi-disk-shaped end plates 11a and 11b attached to both ends of the secondary radiator 11 is arranged. On the secondary radiator 11 side of the primary radiator 10, a plurality of slots 12 are formed extending in the circumferential direction and at equal intervals in the longitudinal direction of the primary radiator 10. The radiation wave from the slot 12 is reflected by the inner peripheral surface 11c of the secondary radiator 11, and is radiated forward.

FIG. 3 is a plan view showing a radiation pattern of the antenna 4. The radiated wave has a main lobe 13 extending forward of the antenna 4 as indicated by the arrow 22 and side lobes 14 symmetrical about the center line L of the main lobe 13. Beam width Δ of main lobe 13
θ becomes narrower as the width W1 of the antenna 4 becomes longer. For example, when the frequency of the transmission signal is 50 GHz, the angle becomes 4 ° when the width W1 is 100 mm, and becomes 200 m.
When it is m, it becomes 2 °.

However, the width W1 has a limit due to the shape of the vehicle body. Therefore, if the depth of the slot 12 is changed to change the intensity distribution of the radio wave radiated from the opening of the antenna 4, that is, if the depth of the slot 12 is fixed, for example, In this case, the electric field intensity distribution becomes flat, and in this case, the beam width Δθ of the main lobe 13 can be narrowed, but the energy corresponding to the narrowing is added to the side lobe 14, 14, the width Δθa is expanded. On the other hand, primary radiator 1
If the slots 12 are formed shallower toward the both ends 10a and 10b and deeper toward the center 10c, the electric field intensity distribution is stronger at the center 10c and weaker at both ends 10a and 10b. Therefore, although the side lobes 14 can be kept small, the beam width Δθ of the main lobes 13 also increases, resulting in poor directivity.

In order to solve such a problem, in the present invention, the beam width Δθ of the main lobe 13 is narrowed, and the object to be detected due to the expanded side lobe 14 is ignored. Therefore, whether the detected object is detected by the main lobe 13 or the side lobe 14 is identified as follows. The antenna 4 is set so that the beam width Δθ of the main lobe 13 is, for example, 2 ° to 5 °, and
4 is formed so as to be generated in a direction oblique from the center line of the main lobe 13 indicated by the reference symbol L by an angle θs of, for example, 5 ° to 10 °.

FIG. 4 is a waveform chart for explaining the operation of discriminating between the main lobe 13 and the side lobe 14. In FIG. FIG.
(1) indicates the displacement speed of the antenna 4 from the stationary state shown in the period T1 to the horizontal direction of the vehicle body shown in the arrow 23 direction perpendicular to the arrow 22 direction in the period T2. For example, first, displacement driving is performed to the right at a speed VE. As a result, when the antenna 4 reaches the predetermined displacement position, the antenna 4 is stopped in the next period T3, and is further driven to move leftward at a speed -VE in the next period T4. The operation represented by such periods T1 to T4 is repeatedly performed at predetermined intervals.

When the object to be detected is detected by the side lobe 14 as shown in FIG. 4B, the output level corresponding to the relative velocity V is caused by the radiation direction of the side lobe 14. Then, a level fluctuation occurs due to the Doppler velocity VD (see FIG. 3) obtained by VEcos θs. On the other hand, the detected object is the main lobe 13
4, an output of a level corresponding to only the relative velocity V is obtained regardless of the displacement of the antenna 4 as shown in FIG. Therefore, whether the detected object is detected by the main lobe 13 or detected by the side lobe 14 is determined based on whether or not a level change corresponding to the displacement of the antenna 4 occurs. be able to.

FIG. 5 is a flowchart for explaining the identification operation as described above. In step n1, the relative speed V obtained from the phase difference between the transmission and reception signals is read. In step n2, the displacement driving of the antenna 4 is started, and in step n3, the displacement speed VE is read. After the relative speed VA with respect to the object to be detected is read again in step n4, the displacement driving of the antenna 4 is stopped in step n5.

At step n6, the relative speeds V, VA
Is obtained. In step n7, the speed difference ΔV is obtained by calculating the Doppler speed V obtained as described above.
D is determined, and if so, in step n8, it is determined that the detected object is detected by the side lobe 14, and the operation is terminated. Otherwise, the detected object is determined in step n9. It is determined that the signal is detected in the main lobe, and the operation ends.

In this way, by determining whether the detected object is detected by the main lobe 13 or by the side lobe 14, a vehicle that runs substantially parallel to an adjacent lane is identified. It is possible to accurately detect only the preceding vehicle ahead without being affected by unnecessary surrounding reflectors.

[0021]

As described above, according to the present invention, the antenna is displaced in the direction intersecting the direction of radio wave emission, and the level corresponding to the Doppler velocity generated when the object to be detected is detected by the side lobe. From whether or not there is a change,
It distinguishes whether the detected object is detected by the main lobe or the side lobe, so that it is not affected by surrounding unnecessary reflectors such as vehicles that are almost parallel in the adjacent lane. Only an object to be detected ahead such as a car can be accurately detected.

[Brief description of the drawings]

FIG. 1 is a block diagram illustrating a radar device 20 according to an embodiment of the present invention and a configuration related thereto.

FIG. 2 is a perspective view of the antenna 4;

FIG. 3 is a plan view for explaining a radiation pattern of the antenna 4;

FIG. 4 is a waveform diagram for explaining an operation of distinguishing a main lobe 13 from a side lobe 14;

FIG. 5 is a flowchart for explaining the identification operation.

[Explanation of symbols]

 Reference Signs List 1 arithmetic circuit 2 drive circuit 3 drive mechanism 4 antenna 5 detection circuit 9 control circuit 20 radar device 21 constant speed traveling device

──────────────────────────────────────────────────続 き Continued on the front page (58) Field surveyed (Int.Cl. ⁷ , DB name) G01S 7/02 G01S 13/93

Claims (1)

(57) [Claims] 1. A radar device for measuring a distance to an object to be detected based on a phase difference between a radio wave radiated from the antenna and a reflected wave from the object, wherein the antenna intersects a radiation direction of the electric wave. A radar device comprising: a displacement unit that displaces in a direction; and a determination unit that determines whether a level variation corresponding to a displacement speed of the antenna has occurred from a received signal of the reflected wave.