JPH05256941A - Fm radar apparatus - Google Patents

Abstract

PURPOSE:To specify the width of the monitoring range of a radar thereby to omit a target outside the range by calculating the two-dimensional position of the target based on the principle of the survey from the measuring results of at least two FM radars. CONSTITUTION:A main body of the FM radar is provided with an FM signal generator circuit 4. A power distributer 5 of the FM radar distributes the FM signal to a transmission signal TS and a local signal LS. A circulator 6 feeds the signal TS to an antenna ANT and a receiving signal RS to a mixer 7. The mixer 7 mixes the signals RS and LS to generate a beat signal BS. The signal BS output from the mixer 7 is converted to a digital signal at an AD converter 8. An FFT circuit 9 reads and processes the digitized data of the signal BS by the high-speed Fourier transform, whereby the beat frequency is spectrally analyzed. A signal processor 3 reads the data of the obtained spectrum thereby to obtain the distance to a searched target.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an FM radar device for measuring the distance to a searched target.

[0002]

2. Description of the Related Art Recently, a frequency of a beat signal obtained by receiving a reflection signal from a target when transmitting a transmission signal by an FM wave whose fundamental frequency is swept and mixing the transmission signal and the reception signal. An FM radar device that measures the distance from the vehicle to the target is mounted on the vehicle, and a search is made as to whether or not there is a forward vehicle in the front area of the vehicle travel. Measurement, for example, the relative speed is calculated from the time change of the measured distance, the appropriate inter-vehicle distance with the preceding vehicle is obtained from the traveling speed of the own vehicle, and the measured relative distance with the preceding vehicle is the appropriate inter-vehicle distance. Some have been developed that notify the danger of a rear-end collision or activate an automatic braking device when the distance falls below the distance.

[0003]

The problem to be solved is that the conventional FM radar device can only measure the distance to the target in the radar monitoring area. For example, the FM radar device Is mounted on the vehicle to search for a target such as a forward vehicle in the front area of the vehicle,
In order to notify the danger level of a collision according to the distance to the searched target or to perform processing such as operating the automatic braking device, an obstacle on the traveling lane of the vehicle becomes an obstacle. Not only the target but also the target on the road shoulder in front of the vehicle and the front vehicle running in the adjacent lane will be searched and processed, and the risk of collision will be notified and the automatic braking device will be activated. There is a problem that is unnecessary.

[0004]

The present invention is, for example, an FM
A radar device is mounted on a vehicle to search for a target object such as a vehicle ahead in the area ahead of the vehicle, and informs of the risk of collision or automatically brakes according to the distance to the searched target object. At the time of performing the processing for operating the device, at least two FMs are arranged at a predetermined interval so that only the target obstacle on the traveling lane of the vehicle can be processed. The radar main body is installed to measure the distance to each target, and the measurement result is used to calculate the two-dimensional position of the target based on the principle of triangulation. The width is specified, and targets outside the specific area width can be excluded.

[0005]

BEST MODE FOR CARRYING OUT THE INVENTION In an FM radar device according to the present invention, as shown in FIG. 1, two FM radar bodies 1 and 2 are arranged so that a predetermined space is provided between the antennas ANT1 and ANT2. , The two-dimensional position of the target is calculated based on the principle of triangulation according to the distance to the target measured by each of the FM radar main bodies 1 and 2, and each FM radar main body 1 and 2 is driven. The signal processing device 3 is composed of a microcomputer for controlling.

Each of the FM radar main bodies 1 and 2 is, for example, as shown in FIG. 2, an FM signal generation circuit 4 for generating an FM signal whose fundamental frequency is swept, and a transmission signal TS and a local signal LS for the FM signal. A power distributor 5 for distributing to
The transmission signal TS is given to the antenna ANT, and the antenna A
A circulator 6 for giving a reception signal RS received by NT to a mixer 7, and a mixer 7 for mixing the reception signal RS and a local signal LS to generate a beat signal BS,
An AD converter 8 for converting the beat signal BS output from the mixer 7 into a digital signal, and an FFT for analyzing the beat frequency spectrum by reading the digitized data of the beat signal BS and performing high-speed Fourier transform. The signal processing device 3 reads the obtained spectrum data and obtains the distance to the searched target.

In the FM radar device according to the present invention,
The FM radar main bodies 1 and 2 are not limited to those that transmit and receive the above-mentioned radio waves, but may be those that transmit and receive a laser beam or ultrasonic waves.

In the thus constructed device, as shown in FIG.
When the distances l ₁ and l ₂ to the target M are respectively measured by the FM radar main bodies 1 and 2 arranged in parallel so that the distance d between the antennas ANT1 and ANT2 becomes predetermined, as shown in FIG. The device 3 is based on each measurement result,
The two-dimensional position of the target M searched for according to the principle of triangulation is calculated as follows.

Now, set the position of one antenna ANT1 to X.
-For the origin (0,0) on the Y coordinate, the other antenna A
When the position of NT2 is taken as (d, 0), the position (x, y) of the target M on the XY coordinates is expressed by the following formula (1),
It can be obtained by solving the simultaneous equations in (2).

X ² + y ² = l ₁ ² (1) (x−d) ² + y ² = l ₂ ² (2)

It should be noted that two solutions of + and-can be obtained as solutions to the simultaneous equations of the equations (1) and (2). The solution of + of them is adopted, and the solution of-which is a pseudo position of the target M is obtained. Don't hire.

As described above, according to the FM radar device of the present invention, the relative distance y to the searched target M and the lateral shift amount x can be obtained.

The two-dimensional position of the target object can be obtained based on the distance to the target object and the direction of the target object, but some FM radar devices detect the direction of the target object. In order to detect the direction of the target, it is necessary to separately install a direction-finding radar such as an amplitude monopulse radar.

In this respect, according to the present invention, by only arranging the FM radar bodies 1 and 2 side by side and measuring the distances to the target M respectively, the position (x, y) can be easily obtained.

Therefore, for example, as shown in FIG.
The FM radar device according to the present invention is mounted on a vehicle 10 to search for a target object that becomes an obstacle in the front area of the vehicle traveling, and the risk of collision with the searched target object under the control of the signal processing device 3. For example, in the signal processing device 3, the traveling lane L of the vehicle 10
By specifying the width of the radar monitoring area according to the above, and looking at the lateral shift amount x of the searched target, the target M searched for within the specific area width can be determined. It becomes possible to target only the target M determined to be within the area width, and to exclude the target M ′ searched outside the specific area width from the processing target. .

[0016]

As described above, in the FM radar device according to the present invention, only the distance to the target F can be measured.
The two-dimensional position of the target can be easily obtained using the M radar main body.

Therefore, according to the present invention, for example, F
When the M radar device is mounted on a vehicle and a process for searching for a target object that is an obstacle for traveling of the vehicle and notifying the risk of collision or operating the automatic braking device is performed,
The width of the radar monitoring area corresponding to the traveling lane of the vehicle is specified, only the target searched inside the specific area width is processed, and the target is searched outside the specific area width. When the target is excluded from the processing, the target of the road ahead of the vehicle or the preceding vehicle running in the adjacent lane may inform the danger of collision or activate the automatic braking device unnecessarily. This has the advantage that it can be prevented.

[Brief description of drawings]

FIG. 1 is a block diagram showing an embodiment of an FM radar device according to the present invention.

FIG. 2 is a block diagram showing a specific configuration example of an FM radar main body in the same embodiment.

FIG. 3 is a diagram showing a relationship between two-dimensional positions of targets according to respective measurement distances to the target by two FM radar main bodies.

FIG. 4 is a diagram showing a target search state in a forward traveling area of a vehicle equipped with an FM radar device according to the present invention.

[Explanation of symbols]

 1 FM radar main body 2 FM radar main body 3 Signal processing device ANT1, ANT2 Antenna M Target

Claims (1)

[Claims] 1. A distance from a frequency of a beat signal obtained by mixing a transmission signal and a reception signal to a target by receiving a reflection signal from the target when the transmission signal by the FM wave is transmitted. In the FM radar device for measurement,
At least two FM radar main bodies are installed at predetermined intervals, the distances to the target are respectively measured, and a means for calculating the two-dimensional position of the target is calculated from the measurement results based on the principle of triangulation. An FM radar device characterized by the above.