JPH0587914A - Fm radar apparatus - Google Patents

Abstract

PURPOSE:To specify the position of a target detected in the monitoring area of a radar by transmitting beams of different main lobes in a manner to be partly overlapped, detecting the reflecting beams from the target, and detecting the direction of the target based on the level of the beat frequency signals obtained in the time sharing fashion. CONSTITUTION:The projecting direction of each beam B1, B2 is set so that the beams are partly overlapped. The levels of the detecting signals Sa, Sb when main bodies 1A, 1B of the radar devices detect a target O within the area where the beams are overlapped are 1a, 1b. The ratio of the sum and difference of the levels (1a-1b)/(1a+1b) is represented by F. A constant S- shaped relationship of characteristic is present between the F value and the directional angle theta of the target O. The relationship between the F and theta is detected and the F-theta characteristic is stored in a memory. The F value is calculated according to the levels 1a, 1b of the signals Sa, Sb when the main bodies 1A, 1B detect the same object O. The directional angle theta of the target O is accordingly detected.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention is a beat obtained by receiving a reflected beam from a target when a beam of an FM wave whose frequency changes with time is transmitted, and mixing the transmitted and received beams. The present invention relates to an FM radar device that detects a target based on a frequency signal.

[0002]

2. Description of the Related Art Conventionally, an FM-CW radar device is mounted on an automobile so as to detect a target object which is an obstacle for traveling of the vehicle and give the detection information to a driver. The device sends a beam that is frequency-modulated at a fixed period, and sends it when a reflected beam from the target is received.
It is only to measure the distance from the frequency of the beat signal generated between the reception beams to the target and give the distance information of the detected target.

[0003]

The problem to be solved is that only information on the distance of the target detected in the radar monitoring area can be obtained, and the position of the target in the radar monitoring area cannot be specified. Is.

[0004]

The present invention is obtained by receiving a reflected beam from a target when a beam of an FM wave whose frequency changes with time is transmitted, and mixing the transmitted and received beams. In an FM radar device that detects a target based on a beat frequency signal that is generated, a part of each beam having different main lobes is overlapped so that the position of the detected target can be specified in the radar monitoring area. As described above, each beam is transmitted in a time-division manner, each reflected beam from the target is received, and each target is transmitted in a time-division manner, and the target is based on the level of the beat frequency signal sequentially obtained by reception. The means for detecting the direction is taken.

[0005]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS FIG. 2 shows the structure of a radar device main body 1 when an FM-CW radar device is used.
A carrier wave is given to the sweep oscillator 3 from the sweep oscillator 3, and an FM signal having a predetermined sweep frequency is given from the sweep oscillator 3 to the circulator 5 through the distributor 4 so that the FM signal is emitted from the antenna ANT toward the target O as a radio wave. It has become.

Then, the reflected wave from the target O received by the antenna ANT is given to the mixer 6 through the circulator 5, where it is mixed with the transmission wave given from the distributor 4 and is adjusted in accordance with the relative distance to the target O. The beat frequency signal is generated by the frequency difference between the two, and the beat frequency signal is taken out as the radar detection signal S through the amplifier 7.

When a target is detected by using such a radar device body, a multi-channel system for frequency-analyzing the radar detection signal S is used to detect the target according to the frequency band of each channel, as described below. It is made to detect whether or not there is a target within the distance range.

Now, when there are a plurality of targets having different relative distances in the radar monitoring area, the radar device body 1
From, a radar detection signal S in a state in which signals having a frequency corresponding to the distance to each target and having an amplitude proportional to the reflected wave from each target is mixed is obtained.

The spectrum at that time contains a plurality of frequency components, as shown in FIG. In this case, there are four targets.

Therefore, the entire frequency range of the radar detection signal S is divided into a plurality of frequency bands, and as shown in FIG. 4, each channel CH1 of each divided band.
Band-pass filters 81 to 8n corresponding to CHn are arranged in parallel,
The respective filter outputs are respectively detected by the wave detectors 91 to 9n, and the respective wave detection outputs are switched by switching the switch SW to the microcomputer 1 via the AD converter 10.
1 is read sequentially and the level judgment using the threshold value preset for each channel is performed to detect whether the target is within the distance range according to the frequency band of each channel. Can be done individually.

In such a case, particularly in the present invention, a means for detecting the direction of the detected target is adopted.

The basic principle for detecting the direction of the target will be described below.

Generally, as shown in FIG. 5, the antennas ANT-a, A in the two radar device main bodies 1A, 1B are used.
Each beam B1 and B2 emitted from NT-b has a different main lobe so that the beams B1 and B2 partially overlap each other.
Radar detection signals Sa, when the emission directions of B1 and B2 are set and the target O in the area where the beams overlap is detected by the respective radar device bodies 1A and 1B.
If the levels of Sb are la and lb, and the ratio of the sum and difference of each level (la-lb) / (la + lb) is F,
It is known that the F value and the direction angle θ of the target O have a constant S-shaped characteristic relationship as shown in FIG.

Therefore, if the relationship between F and θ is obtained in advance by actual measurement and the F-θ characteristic is stored in the memory, the radar device main bodies 1A and 1B can be stored.
By calculating the F value according to the levels la and lb of the radar detection signals Sa and Sb when the same target O is respectively detected by, the direction angle θ of the target O at that time can be obtained. become.

FIG. 7 shows an example of a structure in which a plurality of targets can be individually detected together with the directions of the respective targets.

Here, two FM-CW radar devices having the individual detection function of the target having the configuration of FIG. 4 are installed side by side so as to share the microcomputer 11, and the antenna ANT of the radar device main body 1a on one side A. The beam B1 emitted from -a and the radar device body 1b on the other side B
The beam emission direction of each antenna is set so that the beam B2 emitted from the antenna ANT-b of FIG.

The corresponding bandpass filters 81 to 8n on the A and B sides are set to have the same frequency band.

In such a configuration, first, the microcomputer outputs an output signal for each channel when the radar device main body 1a side is in an operating state (the radar device main body 1b side is inoperative at this time). 11 is made to read and the target is detected.

Next, the microcomputer 11 reads the output signal for each channel when the radar device main body 1b side is in the operating state (the radar device main body 1a side is not operating at this time) to detect the target. Let

As a result, the microcomputer 11 finds out the channel in which the target is detected on the same channel on both sides of A and B, and calculates the F value from the level of the output signal of each channel, as described above. According to the F value, the corresponding θ value is read from the table previously set in the internal memory, and the direction angle of the detection target in that channel is obtained.

At this time, the distance to the detected target is obtained by the channel number of the detected target.

Further, when there are a plurality of sets of channels in which the targets are respectively detected in the same channel, that is, when a plurality of targets are detected over different distance ranges, the F value is obtained for each set and the direction is determined. The direction of each target is individually obtained by performing the processing for finding the angle θ.

FIG. 1 shows an FM for optimally implementing the present invention.
A specific configuration example of a CW radar device is shown. Here, in order to simplify the overall configuration, only one radar device main body 1 is provided and the antenna switch ANT-SW is switched so that two Antenna ANT-a, AN
The beams B1 and B2 can be alternately emitted from T-b.

The triangular wave generator 2 is as follows.
A square wave oscillator 21 that generates a square wave signal with a frequency of 50 KHz, a waveform converter 22 that converts the square wave signal into a triangular wave signal, and the triangular wave signal is corrected so that the oscillation frequency in the sweep oscillator 3 changes linearly. And a linearity corrector 23. In sweep oscillator 3, sweep width 4
Generates an FM wave of 00 MHz.

Further, the band pass filter groups 81 to 8 shown in FIG.
n, the detector groups 91 to 9n and the changeover switch SW, instead of the microcomputer 11 to the DA converter 1
A sweep oscillator 13 that sequentially generates frequency signals divided into stages according to each channel designation signal that is sequentially given via 2, and the sweep oscillation frequency signal and a radar detection signal S that is output from the radar device body 1. Of the mixer 14, a bandpass filter 8 that filters the output signal of the mixer 14, and a detector 9 that detects the output of the filter through an amplifier 15.

In the configuration as described above, the antenna switch A is first operated under the control of the microcomputer 11.
After the NT-SW is closed to the contact a side, antenna A
The beam B1 is emitted from the NT-a in a predetermined direction.

At this time, the target detection capability distance range is 1 to 1.
When set to 00 m, the frequency range of the radar detection signal S is 0.267 to 26.7 MHz.

Further, from the microcomputer 11 to DA
A channel designation is issued to the converter 12, and a DC voltage signal suitable for the channel designation is given to the sweep oscillator 13.

The sweep oscillator 13 oscillates 99 kinds of frequency signals divided every 267 KHz within the frequency range of 31.3 to 57.466 MHz according to the channel designation signal.

The frequency signal output from the sweep oscillator 13 and the radar detection signal S are mixed in the mixer 14, and the mixed output is in the pass frequency band 57.733-5.
The band-pass filter 8 of 8.0 MHz filters the filtered frequency signal through the amplifier 15 by the detector 9, and the detected DC voltage signal is the AD converter 10.
Is read into the microcomputer 11 via the.

At this time, the microcomputer 11 uses the DA
The channel designation given to the converter 12 is sequentially changed from 1 to 99, and the AD converter 1 is provided for each channel designation.
The output data of 0 is used and sequentially stored in the internal memory.

Table 1 shows the relationship between the oscillation frequency fc of the sweep oscillator 13, the frequency range fs of the radar detection signal S, and the distance range L to the target for each channel.

[0033]

[Table 1]

Next, the microcomputer 11 closes the antenna switch ANT-SW on the b-contact side to emit a beam B2 from the antenna ANT-b in a predetermined direction, and in the same manner as described above, for each of channels 1 to 99. Store data in internal memory.

When the data of channels 1 to 99 in each of the two groups is stored in this way, the microcomputer 11 performs noise removal processing such as road reflection and clutter for each group, and then the objects in each channel. Targets are individually detected, and as a result, channels in the target detection state are selected.

Then, using the data in both groups for the selected channel, the F value is calculated as described above, the direction angle θ of the corresponding target is determined, and the detected target corresponding to the number of channels is obtained. The data of the distance L and the data of the direction angle θ are output to the outside.

[0037]

As described above, the FM radar device according to the present invention receives the reflected beam from the target when the beam of the FM wave whose frequency changes with time is transmitted,
When detecting a target based on the beat signal obtained by mixing the transmitted and received beams, not only the distance to the detected target but also the direction of the detected target can be detected. In this way, each beam is transmitted in a time division manner so that a part of each beam having different main lobes overlaps, and each reflected beam from the target is received respectively. , The direction of the target is detected based on the level of the beat signal sequentially obtained by the reception, and it is detected in the radar monitoring area by a simple configuration using only one radar device main body. There is an advantage that the position of the target in the radar monitoring area can be specified by obtaining information on the distance and the direction of the target.

[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 basic configuration example of an FM radar device main body.

FIG. 3 is a diagram showing a frequency spectrum characteristic of a radar detection signal output from the FM radar device main body when there are a plurality of targets.

FIG. 4 is a blog diagram showing a basic configuration for individually detecting a plurality of targets.

FIG. 5 is a block diagram showing a basic configuration for performing direction detection of a target using two radar device main bodies.

FIG. 6 is a diagram showing an f-θ characteristic.

FIG. 7 is a block diagram showing a basic configuration example of an FM radar device according to the present invention.

[Explanation of symbols]

 1 Radar Device Main Body 2 Triangle Wave Generator 3 Sweep Oscillator 4 Divider 5 Circulator 6 Mixer 7 Amplifier 8 Bandpass Filter 9 Detector 10 AD Converter 11 Microcomputer 12 DA Converter 13 Sweep Oscillator 14 Mixer 15 Amplifier

Claims (2)

[Claims] 1. A beat signal obtained by receiving a reflected beam from a target when a beam of an FM wave whose frequency changes with time is transmitted and mixing a transmission signal and a reception signal. In an FM radar device for detecting a target, a means for transmitting each beam in a time division manner so that a part of each beam having a different main lobe is overlapped, and receiving each reflected beam from the target, An FM radar device characterized in that means for detecting the direction of a target is taken based on the level of a beat signal successively obtained by transmitting and receiving each beam in a time division manner. 2. At least two antennas are provided so that main lobes partially overlap with each other, and a means for switching the antennas is provided to switch the antennas.
The FM radar device according to the above-mentioned item 1, wherein the beam is sequentially transmitted from each antenna.