JPH08105963A - Radar device - Google Patents

Abstract

PURPOSE: To detect not only a distance up to a target and relative speed, but also a direction for reducing erroneous judgement by specifying the position of an object on the basis of a distance measured by use of two FM-CW radar sets and properly grasping the state of the object. CONSTITUTION: Radar sections 1 and 2 are mounted on the front of a vehicle at a breadthwise interval. In this case, the chopping wave modulated FM signals of the sections 1 and 2 via oscillators 5 and 12, and modulators 6 and 13 are transmitted from antennae 3 and 10 respectively via directional couplers 4 and 11, and input to mixers 8 and 15, thereby generating reflected and beat signals received from a target with antennae 7 and 14. Signal processing circuits 9 and 16 analyze the beat signals and obtain a distance from the sections 1 and 2 to the target as well as relative speed. Furthermore, CPU 17 defines not only the distance, but also a direction through computation. Also, in order to discriminate an inherent reflected wave from a reflected wave from another radar and eliminate the interference thereof, a modulation period, a transmission frequency, a modulation frequency or the like is changed for use with the radar sections 1 and 2.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a radar device mounted on an automobile and used for collision prevention by measuring an inter-vehicle distance with another vehicle.

[0002]

2. Description of the Related Art It is important for an on-vehicle radar device that measures the distance between vehicles and the relative speed to the preceding vehicle by using a radar and is useful for collision prevention, and to accurately recognize the condition of a target object such as an automobile. It is desirable to be able to recognize targets over a wide range. Japanese Patent Laid-Open No. 62-259077 discloses a vehicle in which a plurality of radars are installed to identify a wide range of targets. This is capable of identifying the direction of a target over a wide range by using a plurality of pairs of monopulse radars whose output beams partially overlap each other.

[0003]

The object of the present invention is to detect not only the distance to the target and the relative speed, but also the direction,
It is an object of the present invention to provide a radar device having a high degree of obstacle discrimination performance with few false judgments.

[0004]

In order to achieve the above object, the position of an object is specified from the distance measured using two FM-CW radars to accurately grasp the state of the object, and In order to prevent the radars from interfering with each other, the FM modulation periods are made different so that erroneous judgments are reduced.

[0005]

In the FM-CW radar device, two FM-CW radars each including a transmitting / receiving antenna, a directional coupler, an oscillator, a modulator, a mixer, a signal processing circuit and an output circuit are installed at both ends in front of the vehicle. And measure the distance from each radar to the target. Since the position of the radar is fixed, the position of the target can be specified from these distances. In order to distinguish the original reflected wave and the reflected wave from the other radar, the modulation cycle, the transmission frequency or the modulation frequency of both radars are changed and used. It is possible to eliminate mutual interference between the radars and to provide a radar device with a small number of erroneous groups.

[0006]

DESCRIPTION OF THE PREFERRED EMBODIMENTS FIG. 1 shows a first FM-CW radar device according to the present invention.
The example of was shown.

Reference numerals 1 and 2 denote first and second radar units, and the radar unit 1 includes a transmitting antenna 3, a directional coupler 4, an oscillator 5, a modulator 6, a receiving antenna 7, a mixer 8 and a signal processing circuit. The radar unit 2 includes a transmitting antenna 10, a directional coupler 11, an oscillator 12, a modulator 13, a receiving antenna 14, a mixer 15, and a signal processing circuit 16. 17 is a CPU,
Reference numeral 18 denotes an output circuit, which includes a speaker 19, a display 20, and the like. In the first and second radar units, a signal FM-modulated with a triangular wave by an oscillator and a modulator is radiated from a transmission antenna via a directional coupler and input to a mixer, reflected by a target object, and received by a reception antenna. A beat signal is generated from the signal input from the beat signal, and the beat signal is input to the signal processing circuit. The signal processing circuit is a filter, A / D converter, D
FFT composed of SP (Digital Signal Processor) etc.
The beat signal is analyzed by, for example, to obtain the distance from the radar unit to the target and the relative speed. Figure 2 shows FM-CW
It is a principle diagram of a radar. FIG. 2A shows the time change of the transmission / reception signal, and the relationship between the frequency of the transmission signal obtained by modulating the frequency of the oscillator with a triangular wave and the time is as shown by the solid line.
The reception signal emitted from the transmission antenna to the outside and reflected from the obstacle is subjected to a time delay due to the distance and a frequency shift corresponding to the relative speed, and becomes like a dotted line. FIG. 2B shows the change over time of the beat signal frequency of the difference between the transmission signal and the reception signal, and the beat signal frequencies of the transmission signal shown by the solid line and the reception signal shown by the dotted line in FIG. As shown by the solid line,
The distance to the obstacle and the relative speed can be determined from the beat signal frequency. The radar unit 1 and the radar unit 2 are provided in the vehicle front portion at intervals in the vehicle width direction, and the distance from the radar units 1 and 2 to the obstacle is calculated by the CPU 17, so that not only the distance but also the direction (azimuth angle). ) Can also be confirmed. In a dangerous situation, the output circuit 18 gives an alarm. However, when a signal radiated from one radar unit is reflected by an obstacle and is received by the other radar unit, it causes erroneous detection, and a countermeasure is required. Interference caused by each radar will be described with reference to FIG. 3 (a) is a bird's-eye view showing two radar units provided in the front of the vehicle and obstacles, FIG. 3 (b) shows the time change of the transmission / reception signal, and FIG. The time change of the beat signal frequency of the difference between the received signals is shown. The signal emitted from the radar 31 provided in the front part of the automobile 30 is reflected by the obstacle 33 and received by the radar 31, but the signal emitted from the radar 32 is also reflected by the obstacle 33 and reflected by the radar 31. Received at the same time. Then, the radar 31 determines that an obstacle exists on the line indicated by the solid line (a). This is shown in FIG.
Explaining in (b) and (c), the reflection signal of the signal emitted from the radar 31 is shown by a dotted line with respect to the transmission signal shown by a solid line in (b), and its beat frequency is shown by a solid line in (c). Further, the reflection signal emitted from the radar 32 and received by the radar 31 is indicated by a chain line in (b) and the beat frequency is indicated by a dotted line in (c). In this case, the radar 31 determines that there are two obstacles. Similarly, in radar 32, radar 31
The radar 32 determines that an obstacle exists on the line indicated by the solid line (b) by the signal emitted from the radar 33 and reflected by the obstacle 33 and received. The signals output from the radars 31 and 32 cause the radar device to make an erroneous determination that an obstacle 34 is present. In order to avoid such an erroneous judgment, in the present invention, if the modulation cycle of one radar is made different as shown by the chain line in FIG. 2A, the beat frequency shown by the chain line in FIG. 2B is obtained. The signal processing circuit can easily discriminate between the reflection signal emitted by itself and the reflection signal of another radar signal, and erroneous judgment can be eliminated.

FIG. 4 illustrates a second embodiment of the present invention.
It is a principle diagram of an FM-CW radar.

In contrast to the first embodiment in which the modulation cycle is different, the modulation frequency is different. Also in the present invention, it is possible to easily discriminate whether the reflected signal emitted by itself is a reflected signal of another radar signal by the signal processing circuit, and it is possible to eliminate erroneous determination.

FIG. 5 shows a third embodiment. In FIG. 5, components having the same operations as those of the first embodiment shown in FIG. 1 are designated by the same reference numerals. 5, 40 and 41 are filters, 42 and 43 are signal processing circuits, and 44 and 45 are triangular wave generation circuits. In the embodiment of FIG. 5, the transmission frequencies of the transmitters 5 and 12 of the radar 1 and the radar 2 are made different so as to eliminate the false alarm due to the signals of the radars of each other. When the transmission / reception band is limited, as shown in FIG.
_m1, so f _m2 do not overlap, the triangular-wave generating circuit 44,
It is necessary to synchronize 45 and select the cutoff frequencies of the filters 40 and 41.

FIG. 7 shows a fourth embodiment of the radar device. In FIG. 7, the same reference numerals are given to those having the same operations as those in the embodiment of FIG. 7 is different from FIG. 5 in that the triangular wave generation circuit 50 is used commonly for the radars 1 and 2.

In the embodiments of FIGS. 5 and 7, unnecessary signals from other radars can be eliminated to reduce false alarms.

Up to now, reduction of mutual interference when a plurality of radars are mounted on the same vehicle has been described. However, regarding reduction of interference from radars mounted on other vehicles such as oncoming vehicles, the modulation cycle, the modulation frequency, or the transmission may be used. It can be dealt with by switching the frequency quickly.

FIG. 8 shows a fifth embodiment of the radar device. In FIG. 8, the same reference numerals are given to those performing the same operation as in the first embodiment of FIG. The difference from the first embodiment is that an image receiving unit 60 including a camera unit 61 and an image signal processing unit 62 is provided in addition to the radars 1 and 2.
By recognizing the direction of the obstacle from the image and combining it with the radar, a high-performance radar device with less malfunction can be provided.

FIG. 9 shows a sixth embodiment of the radar device. In FIG. 9, 70 is an antenna, 71 is an antenna switching circuit, 72 is a radar, 73 is a navigation device, 74 is a sensor, and 75 is an output circuit. The present invention is a radar device that obtains position information from a position sensor such as GPS, and obtains information such as road width in a navigation device based on this position information and switches antennas. Radar with high safety by narrowing the directivity of the antenna on a wide road with multiple lanes and widening the directivity of the antenna when traveling on a narrow road so that pedestrians can be identified. A device can be provided.

[0016]

According to the present invention, the first and second radar units are provided at the front of the vehicle at intervals in the vehicle width direction, and the distances from the respective radar units to the obstacles are obtained. In addition to determining the direction (azimuth), it is possible to provide a radar device with less misjudgment by avoiding mutual interference by making the modulation periods of the radar units different.

[Brief description of drawings]

FIG. 1 is a diagram showing a first embodiment of the present invention.

FIG. 2 is a principle diagram of an FM-CW system for explaining a first embodiment.

FIG. 3 is an explanatory diagram of a conventional problem.

FIG. 4 is a principle diagram of an FM-CW system for explaining a second embodiment of the present invention.

FIG. 5 is a diagram showing a third embodiment of the present invention.

FIG. 6 is an explanatory diagram of a third embodiment.

FIG. 7 is a diagram showing a fourth embodiment of the present invention.

FIG. 8 is a diagram showing a fifth embodiment of the present invention.

FIG. 9 is a diagram showing a sixth embodiment of the present invention.

[Description of Codes] 1 ... First radar section, 2 ... Second radar section, 3, 10 ... Transmitting antenna, 4, 11 ... Directional coupler, 5, 12 ... Oscillator, 6, 13 ... Modulator, 7, 14 ... Receiving antenna, 8, 15 ... Mixer, 9, 16 ... Signal processing circuit, 17 ... CPU, 18 ... Output circuit.

Claims (8)

[Claims] 1. An FM-CW type radar, comprising first and second radar sections comprising an antenna, a directional coupler, an oscillator, a modulator, a modulation control circuit, a mixer, and a signal processing circuit, and A radar device comprising an arithmetic circuit for processing signals from these radar units and an output circuit for issuing an alarm, wherein the FM modulation periods of the first and second radar units are different. 2. An FM-CW type radar, comprising first and second radar sections each comprising an antenna, a directional coupler, an oscillator, a modulator, a modulation control circuit, a mixer, and a signal processing circuit, and A radar device comprising an arithmetic circuit for processing signals from these radar units and an output circuit for issuing an alarm, wherein the first and second radar units have different FM modulation frequencies. 3. An FM-CW type radar, comprising first and second radar sections each comprising an antenna, a directional coupler, an oscillator, a modulator, a modulation control circuit, a mixer, and a signal processing circuit, and A radar device comprising an arithmetic circuit for processing signals from these radar units and an output circuit for issuing an alarm, wherein the carrier frequencies of the first and second radar units are different. 4. The radar apparatus according to claim 3, wherein each of the signal processing circuits includes first and second triangular wave generating circuits and these triangular wave generating circuits are used in synchronization with each other. 5. A radar device, wherein the triangular wave generating circuit according to claim 4 is commonly used for first and second radar sections. 6. The radar device according to claim 1, wherein the signal processing circuit performs signal processing by FFT. 7. A radar apparatus comprising an image signal receiving section including a camera section and an image signal processing circuit, first and second radar sections, an arithmetic circuit and an output circuit. 8. An antenna, an antenna switching circuit, a radar section, a navigation device, a sensor capable of identifying a vehicle position, and an output circuit. The antenna switching circuit is controlled by road information from the navigation device to control the directivity of the antenna. A radar device characterized by switching.