JPS6254189A - On-vehicle random modulation radar equipment - Google Patents

Abstract

PURPOSE:To detect a preceding vehicle exactly at high distance resolution and keep distance between vehicles properly and stably by obtaining correlative value between each phase shift signal phase shifted by a phase shifter and a reflection signal received by a receiver. CONSTITUTION:Clock signals of specified time interval generated by a clock signal generator 1 is divided by a frequency divider 3 and frequency divided signals of specified period are generated. An (m) series generator 5 forms (m) series pulse signals from the frequency divided signals and transmits laser light basing on the (m) series pulse signals from a transmitter 7 to, for instance, frontward of a vehicle. A phase shifter 13 phase shifts the (m) series pulse signals by clock signals. Correlative value between each phase shifted phase shift signal and received signals from a reflecting body received by a receiver 9 is obtained by a correlating device 15, and the distance to the reflecting body is calculated by an arithmetic unit 17 form the phase shift signal that makes the correlative value maximum.

Description

[Detailed Description of the Invention] [Technical Field of the Invention] This invention transmits random pulse electromagnetic waves, for example, in front of a vehicle, receives a reflected signal of this electromagnetic wave from a preceding vehicle, and processes the process from transmitting the electromagnetic wave to receiving the reflected signal. The present invention relates to a random modulation radar device for a vehicle that measures the distance to a preceding vehicle based on the propagation delay time of the vehicle.

[Technical Background of the Invention and Problems Therewith] Radar devices that use correlation technology to detect reflected signals from the preceding vehicle have been developed in recent years in radar devices that detect a preceding vehicle or the like existing in front of the vehicle. Radar R'P? using such correlation technology? For example, "Precision Machinery" Vol. 33 No. 7 (196
7), pages 482-489.

FIG. 4 is an example of a conventional random modulation radar device for a vehicle that utilizes such a correlation technique. This random modulation radar device for a vehicle uses an m-sequence generator 51 that generates an m-sequence pulse signal, and supplies the m-sequence pulse signal generated from the m-sequence generator 51 to a laser diode 55 via a drive circuit 53. However, the laser diode 55 outputs laser light toward the front of the vehicle.

The laser light output from the laser diode 55 hits a preceding vehicle, etc. in front and is reflected back, and this reflected laser light is received by the photodiode 57.
After being amplified by an amplifier 59, it is compared with a reference signal vth by a comparator 61 and converted into a binary signal, which is supplied to one input of an exclusive OR circuit 63. The m-sequence generator 51 is composed of a four-stage shift register 75 and an exclusive OR circuit 77, and is supplied with a clock signal having a period τ from a clock signal generator 65. Further, the m-sequence pulse signal outputted from the m-sequence generator 51 is transmitted to the phase shifter 6.
7, this phaser 67 is supplied to the clock signal generator 6
The period τ of the clock signal is determined by the clock signal from 5.
An integer multiple of 1 pulse width τ of the m-sequence pulse signal, that is, an m-sequence pulse signal whose phase is delayed by 01τ, 2τ, 3τ, etc., is output, and the m-sequence pulse whose phase is sequentially delayed is output. The signal is supplied to the other input of the exclusive OR circuit 63. This exclusive OR circuit 63 is
When the phase-delayed m-sequence pulse signal and the reflected signal converted into 21a by the comparator 61 are at the same level, that is, when both signals are at a high level or a low level, a low level signal is output, and a signal at a different level is output. If one signal is high and the other signal is low,
Outputs a high level signal. The output of the exclusive OR circuit 63 is connected to six monostable multi-by-by breaks, which are activated by the clock signal from the clock signal generator 65 in the case of a low level signal from the exclusive-OR circuit 63. triggered, the pulse width is half of one pulse width τ of the m-sequence pulse signal (
outputs a pulse signal of τ/2). That is, this monostable multivibrator 69 outputs a pulse signal when the levels of the m-sequence pulse signal with each phase delayed and the binarized reflected signal are the same, and this output pulse signal is counted by the counter 71. ; [Number results are RA Ivl
73. In addition, the shift register 75 of the m-sequence generator 57, the phase shifter 67, the monostable multi-by-break 69, the counter 1, and the RAM
73 operates synchronously with a clock signal from a clock signal generator 65.

In the conventional vehicle random modulation radar device configured as described above, the counting results of the counter 71 are stored in the RAM 73 for each phase-delayed m-sequence pulse signal. It is possible to detect m-sequence pulse signals corresponding to large counting results. At the time when this m-sequence pulse signal is generated, it can be determined that the reflected signal from the preceding vehicle has been received by the photodiode 57, so from the delay time of the phase of this m-sequence pulse signal, the preceding vehicle, which is a reflector, It is possible to exclude the distance up to.

Such a random modulation radar device for vehicles has a significantly improved noise margin compared to the known giant pulse modulation laser radar system, and has a lower laser diode output and cost, and a lower cost laser diode drive circuit. It has the unique feature of being able to be simplified and streamlined.

However, when this conventional random modulation radar device for vehicles is used in conjunction with a preceding vehicle automatic tracking control device to configure a preceding vehicle's own initial tracking device, when the preceding vehicle that is being followed enters a curved road, for example, the own vehicle It is necessary to increase the photodiode chip area in the horizontal direction so that the vehicle in front can be captured even when the vehicle turns left or right from the front, and the photodiode that receives reflected light can secure a field of view. When the chip area of the photodiode is increased, the rise time of the light-receiving signal increases in proportion to the chip area. The increase in this rise time is, for example, 1Qnse.
However, the pulse width τ of the m-sequence pulse signal transmitted from the laser diode for the light reception signal having this increased rise time can be increased to some extent, for example, 66 cm.
It is necessary to select approximately n5ec.

By the way, as mentioned above, the pulse width of the m-sequence pulse signal determines the ranging resolution for measuring the distance to the preceding vehicle, so the pulse width τ of the m-sequence pulse signal is set to 6.
If 6n5ec is used, this distance measurement resolution will be equivalent to 10 meters, but this value is considerably larger than the distance measurement resolution of 1-2 meters that is considered appropriate for automatic tracking of the preceding vehicle. Therefore, there is a problem in that an appropriate tracking operation cannot be performed while maintaining an appropriate and stable inter-vehicle distance with the preceding vehicle.

[Objective of the Invention 1 This invention has been made in view of the above, and its purpose is to provide a random modulation for a vehicle that can obtain high ranging resolution and accurately detect a preceding vehicle. Its purpose is to provide radar equipment.

[Main points of the invention] In order to achieve the above object, a random pulse of electromagnetic waves is transmitted, a reflected signal of this electromagnetic wave is received by a reflector, and the transmission delay time Ift from the transmission of the electromagnetic wave to the reception of the reflected signal is determined. In a random modulation radar device for a vehicle that measures the distance to a random pulse generator that generates a random pulse signal based on the frequency divided signal; a transmitter that transmits an electromagnetic wave according to the random pulse signal; a receiver that receives a signal reflected by an electromagnetic wave reflector; a phase shifter that shifts the phase of the random pulse signal using the clock signal; and a phase shifter that shifts the phase of the random pulse signal using the clock signal; The gist of the present invention is to include a correlator that calculates a correlation value with a reflected signal, and an arithmetic unit that calculates the distance from the phase shift signal with the maximum correlation value to the reflector.

[Embodiments of the invention] Hereinafter, the present invention will be explained in detail using the drawings.

FIG. 1 is a circuit block diagram of a random modulation radar device for a vehicle according to an embodiment of the present invention.

The vehicular random modulation radar device shown in the figure is configured to pass a short period clock signal from a clock signal generator 1 to a frequency divider 3.
The m-sequence generator 5 forms an m-sequence pulse signal from the frequency-divided signal divided by 70, and the transmitter 7 transmits a laser beam based on the m-sequence pulse signal, for example, to the front of the vehicle.
The l-series pulse signal phase shifter 13 carries out a phase shift of 1 to 1,
The correlation value between each phase-shifted signal and the signal received from the reflector received by the receiver 9 is obtained by the correlator 15, and the distance to the reflector is calculated from the correlation value by the calculator 17. There is.

The clock signal generator 1 has a frequency of 150M1-1z.

A clock signal with a period τ=6,7 nsec is generated.

This clock signal is supplied to the frequency divider 3 and divided by 10, and is also supplied to the monostable multivibrator 33 of the phase shifter 13 and the correlator 15 for synchronization. The counter 3 of the correlator 15 is also added to the counter 11'1
9 is supplied, and each time this reset signal is supplied, the m-sequence pulse signal from the n1-sequence generator 5 is phase-shifted by 6.7 nsec.
The aim is to obtain a ranging resolution equivalent to m (meters). The frequency divider 3 divides the clock No. 13 of the clock signal generator 1- by 10, and has a frequency of 15MH2 and a period of 67.
Generates a frequency-divided signal of n5ec. This period 67 n5
The frequency-divided signal of ec corresponds to a ranging resolution of 10 m (meters), and is supplied to the m-sequence generator 5 and the counter 39 of the correlator 15. The m-sequence generator 5 is composed of a four-stage shift register 19 and an exclusive OR circuit 21, and is based on the frequency-divided signal supplied from the frequency divider 3.
'-1)X10r (67nsec) = 1μsec
m-sequence pulse signals with a period of 15 pulses are continuously generated with a pulse signal of 67 n5ec.

This m-sequence pulse signal is a pulse signal having a waveform as shown in FIG. 2(a).

This m-sequence pulse signal is supplied from the m-sequence generator 5 to the transmitter 7 and the phase shifter 13. The m-sequence pulse signal supplied to the transmitter 7 drives the laser diode 25 via the drive circuit 23, and laser light is output from the laser diode 25 toward the front of the vehicle as a transmission signal.

This transmitted signal hits a reflector such as a vehicle or a preceding vehicle and is reflected, and this reflected signal is received as a received signal by the photodiode 27 of the receiver 9, amplified by the amplifier 29, and then reflected by the comparator 11. supplied to one input. The other input of the comparator 11 has a reference signal v
th is supplied, and the received signal supplied to one input of the comparator 11 is compared with the reference signal vth in the comparator 11 and binarized, and this binarized received signal is converted to the exclusive logic of the correlation 315. It is supplied to one input of the sum circuit 31.

The phase shifter 13 shifts the phase of the m-sequence pulse signal supplied from the m-sequence generator 5 by 6.7 nsec, that is, by 1 m in distance, every time the reset signal is supplied from the counter 39 of the correlator 15. The phase shifter 13 continues to output the phase delay signal having the same phase delay time until the reset signal is supplied.

Each phase-shifted phase delayed signal is supplied to the other input of the exclusive OR circuit 31. Exclusive OR circuit 31
calculates the exclusive OR of the received signal supplied from the comparator 11 and each phase delayed signal supplied from the exclusive OR circuit 31, and outputs a low level signal when the levels of both signals are the same, and outputs a low level signal when the levels are different. output a high level signal.

The output of the exclusive OR circuit 31 is connected to a monostable multivibrator 33, and the monostable multivibrator 33 activates the clock signal generator 1 when a low level signal is supplied from the exclusive OR circuit 31. When a clock signal is supplied from the device, it is triggered and outputs a pulse signal. This pulse signal is counted by a counter 35. This counting operation in the counter 35 is continuously performed during the reset period until the reset signal is generated from the counter 39, that is, during the period when the phase shifter 13 is set to a predetermined phase delay time by the reset signal. Thus, the correlation value between the set one-phase delayed signal and the received signal is determined as the count value of the counter 35. After the correlation value between a certain phase delayed signal and the received signal is determined in this way, when the next reset signal is generated from the counter 39, the counting result counted by the counter 35 is transferred to the RAM 37 and stored. At step b, the count contents of the counter 35 are cleared. At the same time, the reset signal is supplied to the phase shifter 13, and the phase delay time of the phase shifter 13 is set to 6°70 seconds.
That is, the distance is changed by 1 m, and the correlation between the phase-delayed signal of this phase-delay time and the received signal is similarly determined as the word value of the counter 35, and this 81 value is stored in the RAM 37.

That is, the counter 39 generates a reset signal every time it counts 104 of the frequency divided signal, and this reset period is 67 nsec x 10' = 667 μsec in time.
During this reset period of 667 μsec, the correlation between the same phase delayed signal, for example, a phase delayed signal of 0 nSec (OIll) and the received signal is determined by the correlator 15, and in the next reset period, the correlation between the same phase delayed signal of 0 nSec (OIll) and the received signal is Correlation with phase delayed signal, further 5.7x2ns in next reset period
The correlation with the phase delayed signal of ec(2,m) is 6.7X149nsec (149m
) with the phase-delayed signal. This operation ranges from Om to 1ram to 149i+ with distance measurement resolution of 15
0 reset period is repeated, 667 μsec xl 50
=107tlsac 171 That is, the count value corresponding to each phase shift io, 1.2-149n+ is stored in the RAM 37 every 1QQmsec, and this count value is read by the calculator 17 to calculate the distance to the reflector. put out

The vehicle random modulation radar device is configured as described above. Next, the effect will be explained.

The clock signal from clock signal generator 1 is passed through frequency divider 3
This frequency-divided signal is counted by a counter 39 and is supplied to the m-series generator 5, and the m-series pulse signal from the m-series generator 5 is sent to the laser diode 25 via the drive circuit 23. Supplied, laser diode 25
From there, a laser beam transmission signal as shown in FIG. 2(a) is output to the front of the vehicle. A reflected signal from a reflector such as a preceding vehicle located in front of the vehicle is received by a photodiode 27, and this received signal is supplied to a comparator 11 via an amplifier 29, where it is binarized, and an exclusive OR circuit 31-
supplied to Also, at the same time as this operation, the m-sequence generator 5
The m-sequence pulse signal of
A phase delayed signal of eC(Om) is output for a period of 667 μsec until the reset signal of the counter 39 is supplied, and this phase delayed signal is exclusive ORed with the received signal by the exclusive OR circuit 31.

Assuming that there is a preceding vehicle 45m ahead of the vehicle, the received signal is received with a delay of 3 Q Q n5ec from the transmitted signal, as shown in (n) in Figure 2, and this received signal is first The exclusive OR circuit 31 calculates the exclusive OR with the phase delayed signal of 0 nsec (0111>) ((a) in FIG. 2).
In this case, a low level output signal is supplied to the monostable multi-byte break 33 when this phase-delayed signal and the receiver 5 signal are at the same level, that is, both are at a high level or a low level.

When the monostable multivibrator 33 is supplied with this low-level signal clock (No. 5) as described above, it is triggered by this and generates an output pulse. This output pulse is counted by the counter 35. The counting operation by the counter 35 is continued during the reset period when the reset signal is supplied from the counter 39. As a result, the correlation between this phase delayed signal and the received signal is formed as the total a value of the counter 35. .

Next, when a reset signal is generated from the counter 39, the count value of the counter 35 is transferred to the RAM 37 and stored therein, and the phase shifter 13 is activated with a phase delay time of 6.7 nsec.
(1m), repeat the same operation as described above for this phase delayed signal until the next reset signal is generated, and the correlation between this phase delayed signal and the received signal is counted as the count value of the counter 35. This count value is stored in the RAM 37 by the next reset signal.

Similarly, each time a reset signal is generated, the phase delay time of the phase shifter 13 is (3,7n5ecx 2 (2m),
6, 7x3nsec (3m), ・6. 7x 1
49nsec (149m) from 0Ill to 1
49 m, the counter 35 calculates the correlation between each phase delayed signal and the received signal as shown in (a) to (m), . . . in FIG. The count values are obtained and each of these count values is recorded in the RAM 37 in correspondence with each phase delayed signal.

J: Each phase delayed signal Qnsec (Om)
, 6.7nsec(1+) , 6.7X2nsec(
2m >, ... 6.7x149 (149m) respectively reset period, i.e. 67X 10'
The correlation with the received signal for a period of n5ec=667 μsec is stored in the RAM 37 as a count 11fi.

And 667x150μsec = 100msec
All totals &! ! After finishing the operation, RAM3
7, each phase lag (the count value stored corresponding to number i is read by the arithmetic unit 17, the phase lag signal corresponding to the maximum counting theory is detected from among these count values, and the phase lag signal of this phase lag signal is The distance to the preceding vehicle, which is a reflector, can be calculated from the phase delay time.As in the current example, 45n
+6.7X45nse if there is a preceding vehicle in front
The maximum count value appears in the case of a phase delayed signal of c (45m), and from this count value it is detected that the preceding vehicle is 45m ahead. Note that if there are multiple values with the same maximum count value stored in the RAM 37, the 3I that exists in the center of the multiple maximum values
It is sufficient to determine the maximum value for several ships.

As mentioned above, one measurement cycle is used to calculate the distance to the preceding vehicle from the correlation of all phase delay signals.
Although QQmsec is set, this value of 100m5ec is a sufficient value even when this random modulation radar device for a vehicle is applied to a preceding vehicle automatic tracking device, for example.

In the above embodiment, in order to obtain the correlation between each phase-delayed signal and the received signal, it is necessary to determine the correlation between each phase-delayed signal and the received signal when the level of each phase-delayed signal and the received signal is the same according to the output No. 3 from the exclusive OR circuit 37. , the monostable multivibrator 33 is triggered to generate output pulses, and the output pulses are counted to obtain a correlation value. However, the method is not limited to this method, and other embodiments include, for example, As a result of the output signal from the exclusive OR circuit 31, if the levels of each phase delayed signal and the received signal are the same, the counting operation in the counter 35 is increased, and if the levels are different, the counting operation is performed in the counter 35 to count down. A correlation value may be obtained from the counting results. The numbers shown to the right of each waveform in FIG. 2 indicate the count values of such counting, and FIG. 3 is a graph of these count values. As can be seen from these figures, if there is a preceding vehicle 45m ahead as in the above example,
The maximum count value of 22X667 exists in the range from 41m to 49m, centering on 45m, and the other counts 1+fi are -1,
-4, 7, which is very small compared to the maximum count value, and most of the time the value is -4.

Therefore, it is detected that the preceding vehicle is 45 m ahead of the center of the maximum count value between 41 m and 49 m.

[Effects of the Invention] As explained above, according to the present invention, the pulse width of the random pulse signal, which is the original pulse of the electromagnetic wave transmitted from the transmitter, is determined by the clock signal generation so that the performance of the transmitter can be taken into consideration. A random pulse signal having a pulse width of a predetermined period is set to a predetermined period obtained by dividing the clock signal from the device, and a random pulse signal having a pulse width of this predetermined period is used in a phase shifter to obtain a ranging resolution considerably higher than the period of the clock signal by 1q.
Since the distance to the reflector is determined from the correlation value between each short phase-shifted signal and the reflected signal, the response speed of the receiver, such as a photodiode, is Even when using a device with a slow rise time, it is possible to ensure sufficiently high distance measurement resolution, and even when applied to a preceding vehicle automatic tracking system, the preceding vehicle can be accurately detected with high distance measurement resolution. It is possible to maintain an appropriate and stable distance between the vehicle and the vehicle in front of the vehicle to perform appropriate tracking operations, giving the occupants a sense of security and comfort.

[Brief explanation of drawings]

FIG. 1 is a circuit block diagram of a random modulation radar device for a vehicle showing an embodiment of the present invention, FIG. M2 is an operating waveform diagram of the random modulation radar device for a vehicle shown in FIG. 1, and FIG. FIG. 4 is a circuit block diagram of a conventional random modulation radar device for a vehicle. 1... Clock signal generator, 3... Frequency divider, 5...
・m-sequence generator, 7... transmitter, 9... receiver, 1
1...Comparator, 13...Phase shifter, 75...
Correlator, 17... Arithmetic unit, 31... Exclusive OR circuit, 33... Monostable multivibrator, 3
5.39...Counter, 37...RAM.

Claims (1)

[Claims] A random modulation radar device for vehicles that transmits random pulse electromagnetic waves, receives a signal reflected by a reflector of the electromagnetic wave, and measures the distance to the reflector based on the propagation delay time from the transmission of the electromagnetic wave to the reception of the reflected signal. , a clock signal generator that generates a clock signal with a predetermined time interval, a frequency divider that divides the frequency of the clock signal from the clock signal generator and generates a frequency-divided signal with a predetermined period, and the frequency-divided signal. a random pulse generator that generates a random pulse signal based on the random pulse signal; a transmitter that transmits an electromagnetic wave according to the random pulse signal; a receiver that receives a reflected signal of the electromagnetic wave transmitted by the transmitter by a reflector; a phase shifter that shifts the phase of a random pulse signal using the clock signal; a correlator that calculates a correlation value between each phase shift signal phase-shifted by the phase shifter and a reflected signal received by the receiver; 1. A random modulation radar device for a vehicle, comprising: a calculation unit that calculates a distance from a phase shift signal having a maximum value to a reflector.