JPH02212793A - Fm-cw radar - Google Patents

Abstract

PURPOSE:To execute measurement of the distance from an object target at high speed by performing spectrum analysis of a signal in accordance with a frequency difference between transmission and receiving signals with the use of fast Fourier transform. CONSTITUTION:When specified data are stored in an inside memory in an arithmetic control circuit 9, processing of spectrum analysis by high speed Fourier transform is executed with the use of the data. At the time, spectrum distribution information is obtained by a group of level data at each spectrum divided every channel CHx (x=1, 2, 3...) with the use of the spectrum analysis by high speed Fourier transform. The arithmetic control circuit 9 selects a channel of the data which is at a high level state from a plurality of channel data which is performed by the spectrum analysis to find the distance with an object target in accordance with the channel. At this time, whole processing speed does not become slow for filter processing in the case where the spectrum analysis is performed with the use of a conventional band filter.

Description

DETAILED DESCRIPTION OF THE INVENTION TECHNICAL FIELD The present invention relates to an FM-CW radar device FZ that measures the distance to a target object.

Conventional technology Recently, FM-CW radar devices have been installed in automobiles and other heavy moving vehicles to measure distances and relative speeds to other automobiles or obstacles. Systems are being developed to prevent collisions by issuing warnings to the driver and applying automatic brakes when the vehicle enters a dangerous area.

That F 1. , and the operating principle of the X-CW I node.

As shown in Figure 2, the signal -J- of i & real fixed number fo is raised linearly to fO+Δf with a period of 1''m, and then lowered linearly to the original fo. ＝Mo angle wave, L
Perform modulation +i (f m = 1 / Tm is the changing frequency, f is the frequency deviation width), and use that frequency modulation as (tf is the transmission wave) ゛- towards the 1-node monitoring area. Launch [11, Receive the anti+j wave R-・ from the target existing in the monitoring area 8 Comparing the received wave Iζ- with the previous transmitted wave 'r%l on the same time axis, the radio wave Focusing on the fact that the phase shifts according to the round-trip time td and that the current frequency difference fr is proportional to the distance to the target object, we calculate the distance to the target object by measuring the frequency difference fr.1. This is L7.

Further, by determining the temporal change (dx/dj,) of the determined distance (x) to the target, the relative speed can be calculated.

Conventionally, as this type of FM-CW transmitter device, a 411-wavelength radio frequency transmitter according to the frequency difference fr between the transmitting and receiving signals obtained by mixing the transmitting signal Tw and the receiving Ga piece R%l is used.
The frequency of the signal is measured by spectrum analysis based on the principle of frequency measurement.
A similar one has been developed by the same applicant (see Japanese Patent Laid-Open No. 57-201873).

Figure 4 shows the conventional spectrum analysis formula.
・□ Shows the configuration of the radar device.

In the same configuration as 1, in the 5-frequency modulation unit 1, the signal with the fundamental frequency fO that is also applied to the oscillator 3 (') is converted into a modulation signal Sm by a triangular wave from the modulation A 4 generation circuit 2, and is therefore frequency modulated. , the frequency modulated signal output from its oscillator 3 is distributed by a power divider 4, f
Most of it is put into the circulator 5, and a part of it is put into the mixer [the circulator, which is put into each part 3]
The signal received in step 5 is guided to the antenna ANT and is emitted and transmitted as radio waves into free space.

Then, the reflected waves from object @0 are antennas A, N −
r is received by J, and the received signal is circulated by J.
The output from the mixer 6 (No. 4 is amplified by the amplifier 7, and the receiving frequency according to the frequency difference between the transmitted and received signals from the amplifier 7 is A signal of fr is obtained.

Next, the signal at the reception frequency fr and the signal at the local oscillation frequency fv from the local oscillator 17 are mixed in the mixer 10, and the difference (or sum) between the reception frequency fr and the local oscillation frequency fν output from the mixer 10 is The signal with the straddling frequency fd passes through the amplifier 11 and passes through the bandpass filter 12.
given to.

Then, the signal passing through the bandpass filter 12 is sent to the amplifier 13.
The detected voltage signal is converted into digital data by the A/[0 converter 15, and the data is read into the arithmetic control circuit (microcomputer) 9' and stored in the internal memory. is stored in

At that time, D-A conversion is performed by the control output from the arithmetic control circuit 9'! 16, the local oscillation frequency fν in the JJ part oscillator 17 is continuously changed, and the frequency fd of the signal output from the mixer 10 is made variable so as to correspond to a plurality of channels. - The detected voltage obtained by 1 is converted into digital data by the A-D converter 15 and sequentially stored in the internal memory of the arithmetic and control circuit 9', thereby obtaining a data group based on the spectrum 11 analysis.

From the spectrum distribution information, the arithmetic control circuit 9' calculates
Determine the channel where the reception frequency fr and the local oscillation frequency fv resonate and the detected voltage is in a high level state, and calculate the distance to the target according to the value of the reception frequency fr that is in the resonance state at that time. .

However, F by such a conventional spectrum analysis formula
The M-CW radar device includes a mixer 10, an amplifier 11 .2 for performing channel scanning during spectrum analysis. 'l-pass filter I2, amplifier 13, detector 14
, I].A converter 16 and local oscillator 17, the overall configuration is complicated.

Furthermore, in the conventional method, the processing speed of spectrum analysis by channel scanning depends on the passband width of the bandpass filter 12, and the distance resolution is subtracted by 1-f- from the bandpass filter 1:! The narrower the width of the passage area, the slower the processing speed.4.11- The present invention has been made in consideration of the above points, and has a unique configuration. The present invention provides an FM-CW scanner that is capable of quickly performing sub-11 analysis processing. , the signal according to the frequency difference between the sending and receiving times is processed by fast Fourier transform [
It is characterized by one feature of spectrum analysis.

Hereinafter, one embodiment of the present invention will be described in detail with reference to the accompanying drawings.

In the FM-CW radar device according to the present invention, the first
As shown in the figure, the frequency modulation section 1 includes a modulation signal generator 2 that generates a triangular wave modulation signal Sm, and an oscillator 3 that modulates the frequency of a signal with a fundamental frequency fO according to a modulation signal 5I11. The power divider 4 distributes the transmitted signal, and the transmitted signal given from the power divider 1 is transmitted to the antenna 8N'T'' and emitted as a radio wave, which is reflected by the target object O. The received signal from N T is mixed (j to lj,
circulator 5, its reception signal, power divider 4
the mixer 6 that mixes the transmission signal given from the mixer 6;
An amplifier 7 that amplifies the output of the mixer 6 (1), A that converts the output of the amplifier 7 into a digital signal,
-111) Read the digital signal data output from the converter 8 and its A/D converter 8, perform spectrum analysis using fast Fourier transform, and analyze the spectrum from among the first plurality of channel data. It is composed of an arithmetic control circuit (microcomputer) 9, etc., which calculates the distance to the target object O according to the data channel in the high level state, and controls the sampling period of data in the A/■ converter 8. I'm talented.

However, in the case of a lever constructed in this way, the signal is sent from the amplifier 7, as in the case of the construction shown in FIG.

A signal with a reception frequency fr according to the frequency difference between the reception signals is obtained.

In steps 1 and 5, the signal at the reception frequency fr is sampled at a predetermined period by the A-D converter 8 whose sampling period is controlled by a control signal from the arithmetic control circuit 9, and converted into digital data.

The digital data regarding the converted reception frequency ft~ is read into the arithmetic control circuit 9 and stored in the internal memory. When the arithmetic control circuit 9 stores predetermined data in the internal memory, the arithmetic control circuit 9 uses the data to store the predetermined data in the internal memory. Spectrum analysis processing using fast Fourier transform is executed.

At that time, spectrum analysis using fast Fourier transform reveals that channel CHx (X:
1, 2.31 . . . Svek 1 to Ram distribution information can be obtained by a group of level data in each spectrum divided into l.

In FIG. 3, Sr is the antenna A output from the amplifier 7,
Reception frequency f proportional to the distance between N T and target 0
t-Z, that is, the signal at the B1-frequency between the transmitted signal and the received signal.

Note that for spectrum analysis using fast Fourier transform, known methods can be used as they are.

Then, the arithmetic control circuit 9 selects one channel of data that is in a high level state (or data that is in a high level state if there are multiple targets) from among the multiple channel data subjected to spectrum analysis. (multiple channels) and calculate the distance to the target according to those channels.

Specifically, the distance to the target object is determined by knowing the reception frequency fr in the resonance state from the spectrum-analyzed frequency corresponding to the channel of data in the high level state.

Or, subtract the number (=j) from the multiple channels to be spectrum analyzed, and calculate the number Nx of the data channel in the high level state among the multiple channels.
Knowing this, the distance Lx to the target object is determined from the maximum measured distance L m of the target object in the FM-CW radar device, the total number of channels 11 in the spectrum analysis h, and the distance Lx to the target object according to the following equation.

Lx=T, m/n-(1) Furthermore,
The maximum measurement distance T, in is determined by the modulation frequency of the modulation signal 1-t, frequency deviation width, etc.

As described above, according to the present invention, the arithmetic control circuit 9 calculates the receiving frequency f r according to the frequency difference between the transmitted and received signals, which is proportional to the distance between the FM-CW rotor main body and the target object.
Since the calculation is performed by spectrum 1-Ra 11 analysis using fast Fourier transform, the overall processing speed is slow due to filter processing, unlike when performing spectrum 1-Ra 11 analysis using a conventional bandpass filter. This is advantageous in increasing the total number of channels n to be subjected to spectrum analysis and increasing the distance resolution.

In this case, if a microcomputer for high-speed processing is used in the arithmetic and control circuits 9, it becomes possible to perform spectrum analysis at even higher speed. Since the spectrum analysis using the Twolier transform is performed by the arithmetic processing, there is no need for any component to perform channel scanning during the spectrum analysis as in the prior art.

The overall configuration becomes easier. According to the present invention 1, the FT4-CvJ radar device includes a means for analyzing the spectrum of a signal according to the frequency difference between transmitted and received signals by fast Fourier transform, and the spectrum analysis method. 11. Select a channel with data in a high level state from among the plurality of channel data provided. With a simple configuration, spec 1
- The first advantage is that it can quickly process the RAM analysis and quickly determine the distance between the object and the object.
It has two advantages. ,

[Brief explanation of the drawing]

FIG. 1 is a block diagram showing an embodiment of the FM-CW radar device according to the present invention, FIG. 2 is a characteristic diagram of transmitted and received signals in the I''M-CW radar device, and FIG. 3 is a diagram showing the characteristics of the FM-CW radar device.
FIG. 4 is a characteristic diagram showing a signal with a reception frequency ft proportional to the distance to the target in a CW radar device and a channel to be spectrum analyzed.
, 11-1 is a block configuration diagram showing an FM-CW radar device based on an analytical formula. 1. Frequency modulation section 2. Modulation (No. 8 generator 3.
...Oscillator 4...Power divider 5...Circulator 6 Mixer 7 Amplifier 8 ・A・1-) Converter
9 calculation control circuit

Claims (1)

[Claims] 1. A frequency difference between the transmitted and received signals obtained by mixing a transmitted signal obtained by frequency-modulating a fundamental frequency signal according to a modulation signal and a received signal resulting from a reflected wave from a target object. In an FM-CW radar device that calculates the distance to a target from the frequency of a signal according to the frequency difference between transmitted and received signals, means for spectrum analysis of a signal according to the frequency difference between transmitted and received signals by fast Fourier transform, and the spectrum analysis An FM-CW radar apparatus characterized in that the distance between the target object and the target object is determined according to the channel of data in a high level state from among the plurality of channel data obtained. 2. Number the multiple channels whose spectra were analyzed, calculate the channel number Nx of data in a high level state from among the multiple channel data, calculate the maximum measurement distance Lm, and the total number of channels whose spectrum was analyzed. From n, the distance Lx to the target is Lx=Lm
/n.
FM-CW radar device according to the description in Section 1.