JPS6254191A - On-vehicle random modulation radar equipment - Google Patents

Abstract

PURPOSE:To detect a preceding vehicle exactly even when exhaust gas, rain, fog etc. are in front of own vehicle by obtaining a correlative value between reflected signals binary coded reflected signals and phase shift signals phase shifted by a phase shifter by a comparator. CONSTITUTION:Laser light is transmitted from a transmitter 7 responding to random pulse signals generated by an (m) series generator 51 and reflected signals from a reflecting body are received by a receiver 9. A phase shifter 67 phase shifts random pulse signals successively, and a reference signal generating device 33 generates a reference signal of signal level corresponding to the amount of phase shifting of each phase shift signal phase shifted by the phase shifter 67. A comparator 61 compares the reference signal with reflected signals received by a receiver 9 and binary codes the reflected signals. A correlative value of the binary coded reflected signals and phase shift signals phase shifted by the phase shifter 67 is obtained by a correlating device 75 and the distance to the reflecting body is calculated by an arithmetic unit from the phase shift signal that gives maximum correlative value.

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 reflected signals of the N magnetic waves from the preceding vehicle, and receives the reflected signals from the transmission of the electromagnetic waves. 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.

[Technical background of the invention and its problems] In radar devices that detect preceding vehicles, etc. that are present on both sides of the vehicle, a radar device that uses correlation technology to detect reflected signals from the preceding vehicle has been developed in recent years. There is. A radar device using such correlation technology is described, for example, in "Precision Machinery J33 No.7 (1967
2010), pages 482-489, or “Laser Research” 11
Vol., No. 10 (1983) reprint, ``Pseudo Ndam Modulation CW Lidar for Air Pollution Measurement,'' etc.

FIG. 4 is an example of a conventional random modulation radar device for a vehicle that utilizes such a correlation technique. This vehicle random modulation radar device generates m-sequence pulse No. 15.
A sequence generator 51 is used, and the m-sequence pulse signal generated from this m-sequence generation @51 is supplied to a light transmitter 55 consisting of a laser diode or the like via a drive circuit 53 that constitutes a transmitter 7. Laser light is output from the device 55 toward the front of the vehicle. The laser beam output from the light transmitter 55 hits a preceding vehicle, etc. in front of the vehicle and is reflected back. After being amplified by 5, it is compared with the reference No. 18 Vth by a comparator 61 and the result is 2.
m signal and is supplied to one input of the 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 from a clock signal generator 65. Further, the m-sequence pulse signal output from the m-sequence generator 51 is supplied to a phase shifter 67, and this phase shifter 67 uses a clock signal from the clock IZ signal generator 65 to generate an integral multiple of the period τ of the clock signal, i.e. Integer multiples of 1 pulse width of m-sequence pulse fci g, that is, 01τ, 2τ, 3τ,...
・M-sequence pulse f2 whose phase is delayed by 100m, that is, converting this phase delay time into distance, for example, a phase-delayed signal of Qm, a phase-delayed signal of 101Il, a phase-delayed signal of 20+n, ..., 100m The m-sequence pulse signals whose phases are sequentially delayed are supplied to the other input of the exclusive OR circuit 63. In this case, the increment of 10 m in the value that changes from Om, 10 m, 20 m, -, 100 m represents the ranging resolution, and the maximum 100 m
m represents the maximum distance measurement distance. This exclusive OR circuit 63 operates when the phase-delayed m-sequence pulse signal and the reflected signal binarized by the comparator 61 are at the same level, that is, when both signals are both high level or low level. , outputs a low level signal, and when the levels are different, that is, when one signal is high level and the other signal is low level, a high 5 level signal is output. The output of the exclusive OR circuit 63 is supplied to a counter 71, and the counter 71 counts up when the output signal of the exclusive OR circuit 63 is at a low level, and counts down when it is at a high level. The counting operation in J3 of this counter 71 is carried out for a predetermined period of time [Ol
For example, it continues for a period of to = 1 m sec, and after the end of this counting period, the counting result is R as the correlation value of both signals.
It is transferred to AM73 and stored in correspondence with each phase delayed signal. That is, this operation is performed for each of the phase delayed signals of Om, 10m, 20a, . , R.A.
The count value is stored in M73 as a correlation value corresponding to each phase delayed signal. The counting results stored in the RAM 73 are read out by the stopper 77, and the distance to the preceding vehicle, which is the reflector, can be calculated from the phase delay time for the phase delay signal corresponding to the maximum value. It is. Note that the exclusive OR circuit 63 and the counter 7
1. The RAM 73 constitutes a correlator 75 that obtains the correlation value between each phase-delayed signal and the received signal as a count value.

Figure 2 shows the transmission signal transmitted from the light transmitter 55, 0m-1
00m each phase lag 1z, the received signal reflected from the preceding vehicle that is 60m ahead of the vehicle, and the 60m of the vehicle.
In addition to showing the waveforms of received signals reflected from the preceding vehicle existing in front and the exhaust gas existing 20 meters ahead, the counter 71 for each phase delayed signal and each received 1n signal is shown.
This shows a table of the counted values.

The exclusive OR circuit 63 calculates the exclusive OR of the received signal from the preceding vehicle located 60 meters ahead as shown in (m) in FIG. The count value counted in is shown in the table shown in Figure 2 (
1).

This count value is the count value for one cycle of the m-sequence pulse signal, but the count value for the 60IIl phase delayed signal is the largest at 15, and the count values for the other phase delayed signals are all -1. . From this counting result, it can be accurately determined that there is a preceding vehicle 60 meters ahead of the vehicle.

Such a random modulation radar device for a vehicle has a gun gl.
Since the S/N ratio improves according to the processing time, the noise margin is significantly improved, making it possible to reduce the output power and cost of the laser diode, and to reduce the cost and simplify the laser diode drive circuit. It has a soaked character.

However, in such a conventional random modulation radar device for a vehicle, if exhaust gas is present at the same time, for example, 20 meters ahead in addition to the preceding vehicle 60 meters ahead, the presence of the exhaust gas causes the above-mentioned problem with respect to the preceding vehicle 60 meters ahead. There is a problem in that this correlation is disturbed and the preceding vehicle cannot be detected accurately. To be more specific, 60
The reception signals from the preceding vehicle located m ahead and the exhaust gas located 20m ahead become a combined waveform as shown in (b) in Figure 2, and the exclusive waveform of this reception No. 15 and each phase delayed signal The exclusive OR circuit 63 takes the logical sum, and the output is counted by the counter 71. The count value is shown in (ii) in the table of FIG.
) will be the count value shown.

In other words, when observing the count values shown in this table, 60
The count value for +n phase delay No. 15 is 1 as described above.
The count value for the phase-delayed signal of 201!1 increases from -1 to 7, but 50
The count value for the m phase delay signal also increases from -1 to 7, and the maximum value of the count value decreases due to the presence of 111 air gas. There is a problem in that it is not possible to accurately detect the distance between the vehicle and the preceding vehicle in an environment where such conditions exist.

[Objective of the Invention] This invention has been made in view of the above, and its purpose is to accurately detect a preceding vehicle even when there is exhaust gas, rain and dew, etc. in front of the own vehicle. An object of the present invention is to provide a random modulation radar device for a vehicle that can be used in a vehicle.

[Summary 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 time from the transmission of the electromagnetic wave to the reception of the reflected signal is determined to reach the reflector. In a random modulation radar device for a vehicle that measures the distance of a receiver for receiving a signal reflected by an anti-q1 body of electromagnetic waves; a phase shifter for sequentially shifting the phase of the random pulse signal; a reference signal generating means for generating a reference signal of a signal level; a comparator for comparing the reference signal and a reflected signal received by the receiver to binarize the reflected signal; and a comparator for binarizing the reflected signal by the comparator. a correlator that calculates a correlation value between the reflected signal and the phase shift signal g phase-shifted by the phase shifter; and a calculator that calculates the distance from the phase shift signal with the maximum correlation value to the reflector. The gist is to have the following.

[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 differs from the conventional vehicular random modulation radar device shown in FIG. The only difference is that the other configurations are the same.

This reference signal generating means 33 includes a clock signal generator 65
A counter 35 counts clock signals from the counter 35, and predetermined data is stored corresponding to each count value in order to input the counting result of the counter 35 as an address signal and output data corresponding to the reference signal vth. It is composed of a table ROM 37 which is a storage device, and a D/A converter 39 which converts the output data of the table ROM 37 into an analog reference signal vth and supplies it to the comparator 61.

The first quasi-signal generating means 33 attempts to eliminate the influence of the exhaust gas and the like mentioned above by varying the reference signal Vth for the comparator 61 according to the distance to be measured. Generally, the light reception voltage VC when a foul signal is received from the preceding vehicle is expressed by the following equation based on the inter-vehicle distance intersection (Ill) to the preceding vehicle.

Vc=10BVo/History 4...(1) Here, ■0 is the maximum distance lil1 that can be detected by the preceding vehicle
It is equal to the light receiving voltage VO when it exists at 1 m = 100n+ (Vc = Vo ), and by setting the reference signal vth to this voltage VO, the maximum inter-vehicle distance 1i1 [100 m
This means that it is possible to detect the preceding vehicle up to 0.
A reference signal vth was set at . That is, this voltage VO corresponds to the conventional reference signal th.

This light-receiving voltage (O) by the preceding vehicle is mainly determined by the reflex reflector provided at the rear of the preceding vehicle.

On the other hand, the light receiving voltage (■9) due to particles such as exhaust gas, rain, fog, etc. is smaller than the light receiving voltage due to the flex reflector of the vehicle in front, and although it varies depending on the distribution of particles, according to experimental values, it is expressed as the following equation. Ru.

Vq<10'Vo/Sentence 4...(2) Figure 3 is a graph showing the light receiving voltage VC from the preceding vehicle and the light receiving voltage Vg from exhaust gas, etc., but the difference between both light receiving voltages Vc and VC+ is There is a considerable difference between them. Therefore, by setting a new reference signal vth for the comparator 61 between these two light-receiving voltages, it is possible to remove the influence of exhaust gas and the like and extract only the reflected signal from the preceding vehicle.

Therefore, as shown in FIG. 3, this new reference signal vth may be set between the light-receiving voltage VC from the preceding vehicle and the light-receiving voltage g from the exhaust gas or the like.

Further, the reference signal vth is larger than the above voltage ■0 (Vt
Although it is necessary that h≧Vo), this reference signal Vth may be set to a small value (or may be set as shown in the following equation).

Vth = 106Vo / hair 4...(3) That is,
As can be seen from this equation and the graph in Figure 3, if the reference signal vth is varied according to the distance fill to be measured, reflected signals from exhaust gas etc. that do not reach this reference signal vth will be removed, and the Only the signal from the car can be detected.

In this way, the reference signal v[
The case where 11 is varied will be explained. As mentioned above, the phase shifter 67 generates an m-series pulse signal whose phase is delayed by an integer multiple of the period τ of the clock 18 according to the clock signal from the clock signal generator 65.
11 t le, Om, 10m, 20m, 30
m, ..., 100m phase-delayed signals are output, and the exclusive OR of each phase-delayed signal and the reflected signal is calculated to obtain a correlation value corresponding to each distance. Counting output as shown in the following table 0.1.2.3. by the clock signal in synchronization with the phase delayed signal.・・・
・, outputs 10.

In addition, it is sufficient to form the voltage determined by the above equation (3) and the graph of FIG. 3 for the count value corresponding to this distance, that is, the reference signal vth. In the signal generating means 33, data corresponding to the reference signal vth is first set from this count value, and this data is D/A converted to form the reference signal vth.

That is, the count value of the counter 35 is stored in the table ROM.
37 as an address signal to the table ROM 37, and the table ROM 37 outputs data for each address, that is, the count value, as shown in the following table.

L2- The address in this table is the count value of the counter 35, but it is also a value corresponding to the distance to be measured as described above, and 0 in the address is Qm.

1 is 1m, 2 is 20n+, 3 is 3Qm, -10 is 100
m, and for each distance, the third
Data is output so that the voltage vO in the figure changes. That is, at Qm, the voltage ■9 is large, and data corresponding to 100 is output as an absolute 1 shift, at 10 m, data of 7, at 20 m, data of 2, and after 30 m, data corresponding to 100 is output, as can be seen from Figure 3. is 1. When this is converted to the reference signal vth, as can be seen from the previous equation (3), it is 100 Vo even at Om, 7 Vo at 10 m, and 2 0.30 m to 1 at 20 m.
As can be seen from Figure 3, 00m 111 is not affected by exhaust gas, etc., so it is VO.

In this way, the output data from the table ROM 37 corresponding to the voltage V(1 in FIG. 3, that is, the reference signal vth that varies depending on the distance as described above) is supplied to the D/A converter 39 for D/A conversion. A reference signal vth that changes depending on the distance is output.Then, by supplying this reference signal vth to the comparator 61, reflected signals from exhaust gas etc. are removed as described above, and reflected signals from the preceding vehicle are removed. By extracting only the inverse 0=I signal, it is possible to accurately detect the preceding vehicle and the distance to the preceding vehicle.

Note that the counter 35 is a decimal counter as shown in Table 1, and the phase delay τ is τ=100111 (when the next timing of the counter output -10>, that is, the phase delay of τ-Qm is given, The counter 35 is reset to rOJ. Also, the table ROM 3
7 is a ROM having a storage capacity of 24×128, for example.

In addition, in the embodiment described in Section 2, the distance measurement resolution is 1Qm and the maximum detection distance is 100m for simplicity, but the present invention is not limited to this.
It is easy to change the maximum detection distance to 125m or 150m, such as 125m or 150m.
By appropriately selecting the storage capacity of M, it is possible to remove reflected signals from exhaust gas and the like and accurately detect only reflected signals from the preceding vehicle, as in the above embodiments.

[Effects of the Invention] As explained above, according to the present invention, the reflected signal is
Since the level of the reference signal of the comparator for converting into a single signal is varied to a signal level corresponding to the phase shift height of each phase shift signal, that is, to a signal level corresponding to the distance to be measured, this reference signal Reflected signals from exhaust gas, etc. below the level are removed, so there is no influence from exhaust gas, etc., and only reflected signals from the preceding vehicle can be reliably extracted, even in environments where exhaust gas, rain, fog, etc. However, the preceding vehicle and the distance to the preceding vehicle can be accurately detected.

[Brief explanation of the drawing]

FIG. 1 is a circuit block diagram of a random modulation radar device for a vehicle showing an embodiment of the present invention, and FIG. 2 is an operational waveform diagram of the random modulation radar device for a vehicle shown in FIG. 1 and count values for each phase delay signal. FIG. 3 is a graph showing the relationship between the received light voltage and the distance of reflected signals from a preceding vehicle and exhaust gas, and FIG. 4 is a circuit block diagram of a conventional random modulation radar device for vehicles. 7... Transmitter, 9... Receiver, 33... Reference signal generating means, 35... Counter, 37... Table R
OM, 39...D, /A converter, 51...m series generator, 55... Light transmitter, 57... Light receiver, 61
... Comparator, 63 ... Exclusive OR circuit, 6
5... Clock No. 3 generator, 67... Phase shifter, 7
1... Counter, 73... RAM, 75... Correlator, 77... Operator. Patent applicant: Nissan Motor Co., Ltd. Lianhong 1 (m)

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 random pulse generator that generates a random pulse signal, a transmitter that transmits an electromagnetic wave in response to the random pulse signal, a receiver that receives a signal reflected by a reflector of the electromagnetic wave transmitted by the transmitter; a phase shifter that sequentially shifts the phase of a random pulse signal; a reference signal generating means that generates a reference signal having a signal level corresponding to each phase shift amount of each phase shift signal phase-shifted by the phase shifter; a comparator that compares the reflected signal received by the receiver and binarizes the reflected signal; and a phase shift signal whose phase is shifted between the reflected signal binarized by the comparator and the phase shifter by the phase shifter. A random modulation radar device for a vehicle, comprising: a correlator that calculates a correlation value; and an arithmetic unit that calculates a distance from a phase shift signal having the maximum correlation value to a reflector.