JPH02212792A - FM-CW radar device - Google Patents

Abstract

(57) [Summary] This bulletin contains application data before electronic filing, so abstract data is not recorded.

Description

[Detailed description of the invention]

The present invention measures the distance to a target object. Regarding MCW radar equipment. 1. Conventional technology - Bin Recently, FM-c has been used in moving vehicles such as cars and trains. Equipped with a W radar device, it measures the distance and relative speed between other vehicles or obstacles, and when the vehicle enters a dangerous area, it issues a warning to the driver and automatically applies the brakes. A system is being developed to prevent collisions by using the FM-CW radar system4.The operating principle of the FM-CW radar device is as follows. As shown in Fig. 2, the period T
Modulation is performed by a triangular wave that is applied linearly to fo + Δf at m, and then descends linearly to fo (fm
= 1/Tm is the modulation frequency, Δf is the frequency deviation width), and the frequency-modulated signal is transmitted as a transmission wave]. Receive the reflected wave Rty from the target. Comparing the received waves R and w with the previously transmitted (IT wave '1.' v) on the same time axis, the phase shifts according to the round trip time 1d of the radio wave, and the frequency difference fr at that time is Focusing on the fact that it is proportional to the distance, the distance to the target is determined by measuring the frequency difference fr. Also, the temporal change d of the determined distance to the target (x) The relative speed can be determined by calculating x, /dt. Conventionally, in such a 12M-CW radar device, the transmitted signal 1゛ and the received signal R signal are mixed. A device has been developed by the same applicant in which the frequency of a signal according to the frequency difference fr between the transmitted and received signals obtained by is measured by spec.1 to spec.11 analysis based on the principle of determining the heterodyne frequency Δ1. (Unexamined Japanese Patent Publication No. 5
7-201873). However, F by such a conventional spectrum analysis formula
In the M-CW radar device, the radar performance related to the maximum measurement distance and distance resolution when determining the distance to a target object is fixed. In this regard, if an FM-CW radar device is installed in a car or the like and the distance between the vehicle or an obstacle in front is measured and the vehicle's running control is adjusted to tJ, the vehicle's running speed and Adapting to various situations such as mixed driving roads, determining the distance between the target and the target with the maximum all + constant distance and distance resolution, the more optimal vehicle; The present invention of 9.1-1, which makes it possible to control <, .
In order to be able to use the zoom function, the maximum a (11 constant distance) when determining the distance to the target object, Lbi?4
The relationship between the separation and partial resolution is also variable.

[1. 1. Adjust the performance of one node according to the usage conditions. 1, and also provides an FM-CW generator device by a spectrum analyst, so that it can be optimally projected. DESCRIPTION OF THE PREFERRED EMBODIMENTS An embodiment of the present invention will now be described in detail with reference to the accompanying drawings. FIG. 1 shows F according to the spectra 13 analytical formula according to the present invention.
This shows an example of the basic configuration of the M-CW radar device.
FM that takes advantage of the frequency difference between transmitted and received signals
- The frequency of the signal according to the frequency difference between the CW radar main body A and the obtained transmitted and received (1) signals is determined by Svek 1 to Ram analysis based on the principle of heterodyne frequency measurement. FM-CVti radar body 8 and a frequency modulation section]
Smell, i- to oscillator 3! fundamental frequency f +-1
The frequency is modulated according to the triangular wave modulation signal Sm from the oscillator 3, and the frequency-modulated signal output from the oscillator 3 is distributed by the power divider 1. Most of them are circulator 5
and a part of it is given to the mixer 6, respectively. The signal detected by circulator 5 is sent to antenna A N
It is guided by T and emitted as a radio wave into free space. Then, the reflected wave from the target object 0 is received by the antenna A N'r, and the received signal passes through the Zaki collector 5 and is sent to the mixer 6, where it is mixed with the transmitter 100 and sent to the mixer 6. The output signal of is amplified by a preamplifier 7, from which a signal having a reception frequency fz.according to the frequency difference between the transmitted and received signals is obtained. . In addition, the distance measuring section I3 receives a signal of the receiving frequency fr, a signal of the local oscillation frequency [V] from the local oscillator 1, which is mixed in the mixer 8, and a signal of the frequency [d] output from the mixer f8. is passed through an amplifier 9 to a bandpass filter 10 (where only frequency signals in the intermediate frequency band are filtered). , So [5. Then, the signal that has passed through the bandpass filter 10 is passed through the amplifier 11 and sent to the detector 12, and then the detected voltage is output to the converter 13 (4.4 or A.1). The data is converted into the child data and read into the control circuit 14, which consists of Y, and is stored internally in the L memory. In the case of 4, 2), the frequency f of the 411 signal output from the mixer 8 ((is the difference (or sum) of the 4 frequency lτ and the local oscillation frequency fv). According to the frequency of fr-fv=fd (or fv-fr=fd,
The relationship f r + f v = f d) holds true. Therefore, the control signal output from the arithmetic control circuit 14 causes the local oscillator 16 to pass through the 1].A converter 15.
By changing the local oscillation frequency fv of the mixer 8, the frequency fd of the signal output from the mixer 8 can be variably controlled. Therefore, in the control of the arithmetic control circuit 1.1, the local oscillation frequency fv of the local oscillator 16 is made variable, and the third
As shown in the figure, 2. ? +The reception band l1lAW determined by the passband width of the F-band filter 10 is moved from the lower frequency range to the higher frequency range by that bandwidth G,
l, so each time the detected voltage by the detector 12 is A
-I) The converter 13 converts the data into digital data and sequentially stores it in the internal memory of the arithmetic control circuit 1.
The arithmetic control circuit 14 calculates for each reception N+band W when the reception band W is spread over a predetermined range. The data of each detected voltage at 41 (-J) is stored in the internal memory, and finally the detected voltage becomes a high level state from the spectrum 1-ram distribution information. Then, as shown in Figure 3, mark the target ○,
When the detection voltage Vd reaches the Heilbell state, the corresponding local oscillation frequency fv is determined from the number of one (or more) data in -C, and the frequency of the receiving frequency fr, which is in the resonant state at that time, is calculated. Based on the determined frequency, the distance to (1-) (or a plurality of) targets is calculated. At that time, the number of the data where the detection voltage Vd is in the heil bell state is Nx, the maximum measurement distance when calculating the distance to the target is L m, and the number of data in the spectrum 1-ram analysis data group is (2), the distance L x to the target object can be found from the following equation. L x = N x - T, m / n - (
1) Now, the distance resolution, maximum measurement distance, and spectrum analysis processing time (scanning time of reception band W) when measuring the distance to the target object in the I/M-CW radar device using such Spectra 11 analysis formula. ), we get the following. . The propagation speed of radio waves is (・, the frequency deviation width during frequency modulation is Δf, the modulation frequency is fn+, the maximum measurement distance is 1, etc.)
II, the reception d frequency output from mixer 8 when the target is at the maximum measurement distance is frIll, and the Svek 1 ~ Lamb analysis frequency resolution (frequency width in reception band W) is f
W, the number of Subek 1 Hella 12 analyzes (the number of data of Subek 1 Hella analysis data group) is +1, the distance resolution is Qd, etc.
The following formula holds true. . frm=4 Lm・fm・Δf/c −(2) fr
m=n lfv−(3)Qd=L
m/n ++・(4)(2),(
From equations 3) and (4), Qd=c −fw/4 fIlbiΔf −(
5) is obtained. Therefore, from equation (5), when the spectrum analysis frequency resolution fv is constant, the distance resolution Qd can be made variable by changing the modulation frequency fm and the frequency deviation width Δf. Furthermore, from equations (2) and (3'), Lm==n-fv·c/4 fm·Δf l) can be obtained. Therefore, from equation (6), when the spectrum 1 - ram analysis frequency resolution fw and the spectrum 1 - ra 11 analysis number X1 are respectively constant, the modulation frequency fm, the frequency deviation width Δf
By changing , the maximum measurement distance 1'-Ill can be made variable. Further, if the scanning time by the reception band W at the time of SEG1-ram analysis is set to 18, the following equation holds true. ta=n/f residue...(7) Therefore, from equations (2), (3), and (7), ta=4 Lm-
f+l+·Δf/c−fW2− (8) is obtained. The present invention is directed to a spectrum analysis type de-M-CW.
Depending on the characteristics of distance resolution, maximum measurement distance, and spectrum analysis processing time for the radar mounted on the head, there is a means to change the setting of the maximum 1'J fixed distance depending on the situation, its setting ti, and maximum mq setting. By using means for switching to a distance resolution that is determined with a constant ratio to the distance, the distance resolution can be varied over a range from long distances to short distances, and the distance between the target object and the target object can be changed. It is characterized by a zoom function that allows you to perform measurements. At this time, as a means for changing the setting of the maximum measurement distance, for example, the operator issues a command to set the maximum measurement distance from the operation unit (not shown) to the calculation control circuit 1 and 1 to manually set the maximum measurement distance. Further, the arithmetic control circuit 14 reads the signal of the traveling speed V of the vehicle sent from the speed detector, and automatically sets the optimum maximum measurement distance according to the traveling speed V at that time. is also possible. The case where a fixed distance of up to 8I is automatically set according to the vehicle's running speed V will be explained below.1.
- If a CW radar device is installed and the distance between the vehicle in front or the target object such as an obstacle is determined by 1 (II), the necessary detection of the target object by the radar device h + i distance, n is the safe inter-vehicle distance Rs Which [-, j-1 is good. The safe inter-vehicle distance R,s is maximum when the target to be detected is stopped and is at 4, so find the safe vehicle open road 111R,s under that condition. 4. Now,
tl is the time when the driver confirmed the target object, then tl is the time when he stepped on the brake and started decelerating. Furthermore, after the acceleration of the vehicle reaches α (α<0) from 0 and the time is t2, Ll, the vehicle has an acceleration of 11, 611. Suppose that the velocity reaches 0 at 2, and
``r, From time 0 to 11, the vehicle moves at a constant velocity of ~ ·, and from time 11 to t(), the acceleration decreases by 5 in proportion to time from 0 to 6 years. Assuming that T1 (calculate the distance traveled by both vehicles), the distance traveled between time 0 and tl is Ry1.
is Ryl, = v-t 1 . The running part ■Ha12 that takes 1 hour between time t1 and time t12 is Ry2= v (t2~tl,) + α
(t2-t],)2/6 roar. The traveling distance 1 shi 3 from time 12 until the speed reaches 0 is R,y3=-(v+α・t2/2)2/2a1, Therefore, the total traveling distance Ry, Ry = II,, 91 + Ry2-1. -1
At y3(v4;l/2)−(V′/2α)
+ (α・+, 22/24) (α・tl・t2/3) → −
(α・t12/6). Now, considering the actual value, v = 27.8m/S (100K m/H),
t1. =0.75 seconds. If t2-1 seconds, a=-4,9m/S2 (-0,5G), then (α・L22/24), −(α
・tl・t2/3) and (α・tl”/6) terms have sufficiently small values. Therefore, if these terms are omitted, Ry=(v
・tl, / 2 ) - (v ” / 2
α)...(9). [1. Make sure the driver is stationary and 2. Checks the target object.)] The total travel distance RV until the vehicle comes to a stop after stepping on the brake is the maximum safe following distance Rs. , Then, the maximum measurement distance r in the FM-CW radar device,
m is the required detection distance, it should be thicker than n, and for safety, add a certain margin to the required detection distance Ln, Lm-= (11-K) ・Ln-(1
0). Here K is the safety factor. , In that case, the required detection distance is 1. +n or safe following distance R3 is set to 5, so <9>, (
10) From formula, T, l11 = (1+K) ((v-t2)-(v'
/ 2α)) -al) Howl. Here, t2. By setting a and K to constant values that suit the actual situation,
The maximum measured distance is a function of the vehicle's running speed fj, and the maximum measured distance is determined by the running speed. ,,,, m
can be determined. Therefore, in the configuration shown in FIG. 1, the calculation control circuit G at step 19 is executed.In path 14, the signal of the vehicle's traveling speed V sent from the speed detector is read, and the calculation process is carried out again using equation (11). If this is executed, the optimum maximum measurement distance 1i L m will be automatically set according to the vehicle's running speed (2) at that time. In this case, the data for the maximum measured distance L and ■ (based on the calculation results corresponding to each of the vehicle's traveling speeds) are stored in advance in the internal memory, and the data is read from the memory according to the value of the traveling speed V. It is also possible to set the maximum measurement distance m by reading out the maximum measurement distance 1., m. When the maximum measurement distance 1., Il+ is set in this way, the arithmetic control circuit 14 reads (4). ), when the number of spectrum analyzes n is constant, the distance resolution Qd is proportional to the maximum measurement distance T, -m, so the distance resolution fl+1 can be determined. Then, the arithmetic control circuit 14 As mentioned above, by changing the modulation frequency f111 and the frequency deviation width Δf as appropriate, assuming that the frequency resolution f- is constant, the distance resolution can be changed to the determined value 1'!d. In this case, in the present invention, the spec 1
In this case, the relationship between Equations (5) and (8) is such that the Hellam analysis scanning time ↑a is always constant. l・
What J is the modulation frequency f + n and frequency deviation width Δf?
1. By changing either side so that it is inversely proportional to the maximum retirement age 11tT, Il+, the distance resolution Qd is proportional to the maximum measurement distance 1-m and the spectrum analysis scanning time ↑a is kept constant. Can be done. 1. To summarize, according to the present invention, the modulation frequency fm is set while the sube91-ram analysis frequency resolution fw and the spectrum analysis frequency resolution fw are each kept constant. By keeping one of the frequency deviation widths Δf constant L2 and making the other variable, the scanning time t for 1 Hellam analysis can be reduced.
When a is constant and the maximum measurement distance L m is large, the distance to the target is measured with a large distance resolution Qd, that is, with low resolution, and the distance to the target is measured at a short distance where the maximum measurement distance L m is small. In the case of distance, the distance to the target can be measured with a small distance resolution Qd, that is, with high resolution.゛In other words, from long distances to short distances, the range resolution is changed from long/low resolution to high resolution, but IE,
, it becomes possible to emit the zoom function to measure the distance to the target 4. For example, modulation 1) ij
C will explain the case where the wave number f111 is made variable.5 First, the arithmetic control circuit 14 takes in the data of the traveling speed V in light rain, and calculates the maximum nll
+ Fixed distance 1. ．． ．． ．． ．． 1 to find m. Next, the arithmetic control circuit 1.1 uses the above equation based on equation (8) to calculate the modulation frequency f n+. 1 f+n=(c・fu'・ta/−4・Δf)・l
/Tm・(12) Next, the arithmetic and control circuits 1 and 1 calculate the frequency of the modulation signal ""f S m due to the generated shearing knee angle wave if the modulation signal generation circuit 2 or l≧. Then, the arithmetic control circuit 1 reads the spectrum-analyzed take group and performs as described above. to find the distance to the target. Note that specific examples of changing the modulation frequency fm or the frequency shift width Δf will be described below. In order to change the modulation frequency fm, in the present invention, as shown in FIG. 4, when the triangular wave modulation signal Sn1 is equally divided in the time axis direction, frequency data fO,
fl, f3.・Sequentially reads out frequency data from a memory registered in advance, converts the read frequency data into a -C analog voltage signal, and passes the analog voltage signal through a low-pass filter; The means for reproducing the modulated signal by the two-up civil angle wave is changed, and the reading cycle is changed when frequency data is read from the memory. FIG. 5 shows a specific example of the configuration of the modulated signal ";3 generation circuit 2 in the configuration of FIG. Timing 47 is generated from the Y signal generation circuit 22, and the timing signal is not given to the address counter 23, and the frequency data is transferred from the ROM 24 to the counter output. are sequentially read out 5, and the read frequency data is sequentially latched in the launch circuit 2.5 according to the timing signal to the i generation circuit 22 or l, and the latched frequency of the child is・1, r) which is sequentially input to the A converter 26 ・Analog 4/voltage output from the A converter 26 (i'f does not change stepwise as time passes) To achieve this, the analog voltage No. 451 is passed through the Dopper Noir 27, and the change is smoothed out so that it changes in the form of one step upward, or that the steps between each step in the analog voltage signal become almost linear. In the above 2) modulation signal generation circuit',), in the present invention, the clock circuit 21 is configured as shown in the figure.
Crossy complex oscillator (crystal oscillator') 211 and 5 which generates a clock signal with two frequencies fi・ and its clock frequency f+
- is configured with a frequency divider 212 that can change the setting of the N value to 1//N, and the Go to 2 as shown in the diagram.
In addition, depending on the selection command of the distance division function, the control circuit 14 or 1 "j, the traveling speed of the vehicle that entered
From gf to pre-programming, control contents 1'''L
,,, the control circuit A determines the frequency division value N of the frequency divider 212.
', 1. ” A, I is obtained, and the division value N of i′j to 2I2 is incremented by 1 as specified. So, the frequency divider 21 = + - the frequency division fiff N changes 1''), (depending on the point, ■<0 to 1;), 1 or J゛) the frequency factor - the The 16V output when reading out 1-1Fil ) tll is controlled by the phase change, and the variable a frequency f111 changes to )),!゛) to be, to be 7. Furthermore, in order to change the frequency deviation width Δf, in the present invention, as shown in FIG. 4, the frequency data fO, [ Memo I with 1, f3. recorded in advance
J or i) Read out the frequency data sequentially and convert the read frequency data to 1-) A converter A + D Q voltage signal, and then convert it to an analog of E-C and A. Voltage(:
By passing it through a pass filter, a means is taken to regenerate the modulated 'R' signal by an angular wave, and when reading frequency data from the memory, the address range of the reading I2 is changed.・1 In terms of the frame, Figure 5 shows the amount of modulated signal generated!821
As shown in FIG. 7, the address counter <!
Number generation circuit 2! As soon as the timing signal emitted from the counter 231+, the timing signal emitted from the counter 231+, the timing signal emitted from the counter 231+, the timing signal emitted from the counter 231+, No. 1 ri 1: S T': T
tj, get - Number construction circuit 23:) What is the N-adic counter configuration? Under the control of the arithmetic control circuit 1.1, the set value for
,' 2. For example, in response to a selection command for the distance division function inputted from the operation unit shown in the figure [5, not shown], or the calculation control circuit 1.
・The control content t, :, l-, which has been pre-subtracted from the traveling speed of the vehicle which has been read as 1. Therefore, from the arithmetic control circuit 14, the N-adic control is applied to the circuit 2:3:ll. 5-----E1'l A T A 2 is obtained and set to a predetermined value of the N-ary column 1 in the matching circuit 232. In the FM-CW generator device according to the present invention, when a frequency measurement method based on spectrum analysis is used, there is a means for setting a maximum Iff fixed distance, and a means for setting a maximum fixed distance of A means for switching to a distance resolution whose ratio to the measured distance is always constant is determined, thereby making the zoom function shine, and adjusting the usage situation such as the traveling speed of the vehicle equipped with the FM-CW radar device. It has 11 points, which makes it possible to optimally determine the distance to the target with radar performance adapted to the situation.

[Brief explanation of the drawing]

FIG. 1 shows an FM-CW L-tactor device ffi according to the present invention.
A block diagram showing an example of the basic configuration of “
(-)Characteristic diagram of transmitted and received signals in iE in W radar equipment,
Figure 3 shows the distance between the target and the FM CWL-da device.
・Characteristic diagram showing the detected voltage of the receiving frequency and the receiving band according to Spectral 11 analysis, which is proportional to the distance between FIG. 5 is a six-block diagram showing a specific configuration example of the modulation signal generation circuit in the FM-CW radar device according to the present invention, and FIG. 6 is a characteristic diagram showing the frequency gradient at each division point when A block diagram showing a configuration example of a tarok circuit included in a modulation signal generation circuit of an i'' M-CW radar device according to the invention,
FIG. 7 is a block diagram showing an example of the configuration of an address counter in a modulation signal generation circuit of an FM-CW radar device according to the present invention. Frequency modulation section 2, modulation signal generation circuit 3, oscillator 4
...Power divider 5...Circulator 6.8...Mixer 7...Preamplifier 9,11・Amplifier 10
Bandpass filter j2/detector 13/A/1 converter
14.- Arithmetic control circuit 15- D/A converter 1 [)
・Local oscillator 2 clock circuit ′, 2 ties;
(reception signal) generation circuit 23 Atres counter R(,)M latch circuit 26...L]/A converter/pass filter

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. FM-C that measures the distance to the target by determining the frequency of the signal that follows by spectrum analysis.
The double radar device is characterized by having means for setting a maximum measurement distance and means for switching to a distance resolution determined in such a manner that the ratio of the set maximum measurement distance is always constant. FM-CW radar device. 2. The FM according to item 1 above, characterized in that the maximum measurement distance can be manually set arbitrarily.
-CW radar equipment. 3. The maximum measurement distance is calculated from the calculation result to determine the required inter-vehicle distance according to the traveling speed of the vehicle equipped with the FM-CW radar device, and the calculated maximum measurement distance is automatically set. The FM-CW radar device according to the above item 1, characterized in that: 4. The FM-CW radar apparatus according to item 1 above, characterized in that the scanning time in a certain frequency band during spectrum analysis is made constant. 5. As a means of determining distance resolution, the frequency of the target modulation signal corresponding to the set maximum measurement distance is calculated and variably controlled so that the frequency of the modulation signal becomes the determined target value. The FM-CW radar device according to the above item 1, characterized in that: 6. As a means of determining distance resolution, calculate the frequency deviation width in the target modulation signal corresponding to the set maximum measurement distance, and the frequency deviation width in the modulation signal becomes the calculated target value. 2. The FM-CW radar device according to item 1 above, characterized in that the FM-CW radar device is variably controlled as follows. 7. When the modulated signal is equally divided in the time axis direction, the frequency data at each division point is sequentially read from the memory in which it is registered in advance, and the read frequency data is sequentially D/A converted and then low-pass According to the above item 5, the method is characterized in that the modulated signal is reproduced by passing it through a filter, and the frequency of the modulated signal is made variable by changing the reading cycle of the frequency data from the memory. FM-CW radar device. 8. When the modulated signal is equally divided in the time axis direction, the frequency data at each division point is sequentially read from the memory in which it is registered in advance, and the read frequency data is sequentially D/A converted and then low-pass The modulated signal is reproduced by passing it through a filter, and the frequency shift width of the modulated signal is made variable by changing the address range for reading frequency data from the memory. FM- as described in Section 6
CW radar equipment. 9. Item 7 above, characterized in that the period of reading the frequency data from the memory is changed by varying the period of the clock signal given to the address counter that sequentially reads the frequency data from the memory using a frequency divider. FM-CW radar device according to the description. 10. By using an N-ary counter as an address counter that sequentially reads frequency data from the memory according to a clock signal, and by making the N-ary setting value of the counter variable,
9. The FM-CW radar device according to item 8, wherein the address range for reading frequency data from the memory is changed.