JPH0990031A - Device for detecting speed of vehicle - Google Patents

Abstract

PROBLEM TO BE SOLVED: To make a device for detecting speed of vehicle withstand disturbances and interference by eliminating the influence of the multiple paths on the device. SOLUTION: A device for detecting speed of vehicle is provided with two antennas 1 and 2 which radiate radio wave beams by performing spectrum spreading and receive reflected waves, a correlator 35 which specifies the distance between gates passed through by a vehicle based on the time representing the peak value obtained by reversely spreading the modulated signals of received signals, a code generator 37 which generates a code sequence at a fixed speed, a bit delaying section 38 which specifies the distances from the antennas 1 and 2 to the gates by delaying the code sequence used by the correlator 35 for reversely spreading the received signals, and a Doppler filter and amplifier 36 which only extract a Doppler frequency component. A speed computing section 9 calculates the time difference between the time when the vehicle passes through one gate and the time when the vehicle passes through the other gate and, when the vehicle exceeds the speed limit, finds the Doppler speeds of the vehicle with respect to the two radio wave beams and averages the speeds. When the difference between the Doppler speeds is larger than a prescribed value, the section 9 calculates the meandering speed of the vehicle.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a vehicle speed detecting device for detecting speed of a vehicle from the shoulder of a road and performing a speed violation control, and is particularly resistant to all weather conditions, multipath effects, interference and interference, and environment. The present invention relates to a vehicle speed detection device that is compatible with the characteristics.

[0002]

2. Description of the Related Art In a conventional vehicle speed detecting device, two electric coils are embedded in a road at regular intervals, and an electric pulse is induced in these electric coils by a vehicle passing over the electric coils to determine the timing of the electric pulse. Then, the speed of the vehicle was detected. In addition, pulse and FM (Frequency Mo
There is a vehicle speed detection device using a radar system of a dulation) -CW (Continuous Wave) system. When this vehicle speed detection device is fixed and the speed of the vehicle is measured, a frequency-modulated signal is transmitted as a radio wave to the vehicle, and a reception signal reflected from the vehicle is mixed with the transmission signal. The speed of the vehicle is detected by obtaining a signal containing a Doppler frequency component based on the speed with respect to the vehicle, detecting the Doppler frequency component from this signal.

[0003]

However, in the conventional vehicle speed detecting device using the former electric coil, when the vehicle passes diagonally, when the motorcycle passes, etc.
There was a problem that the speed of the vehicle was not detected correctly. Also, in the latter vehicle speed detection device using the radar system,
Since the ability to suppress unnecessary reflected waves from the vicinity of installation is low,
There is a problem that it is easily affected by rainfall and snowfall, and it is difficult to separate each vehicle when multiple vehicles are in close proximity.

Therefore, in view of the above problems, it is an object of the present invention to provide a vehicle speed detecting device which can correctly detect the speed of a vehicle.

[0005]

In order to solve the above problems, the present invention provides a vehicle speed detecting device for reflecting a radio wave to a vehicle traveling straight ahead and detecting the speed of the vehicle based on the reflection information.
Based on two antennas that spread spectrum at a certain angle, emit two radio beams, and receive reflected waves, and the time at which the peak value obtained by despreading the demodulated signals of the received signals by the two antennas is exhibited. , A correlator that specifies the distance width of the gate through which the vehicle passes, a code generator that generates a code sequence at a constant speed to perform spread spectrum and despreading, and because the correlator performs despreading And a Doppler filter and an amplifier for extracting only a Doppler frequency component from the output of the correlator, by delaying the code sequence of 1 by a certain number of bits to specify the distance from the two antennas to the gate through which the vehicle passes. Based on the extracted Doppler frequency component level, the time difference between the passage gates of the vehicle formed by the two radio waves is calculated, and this time is calculated. A time difference / speed determination unit that determines whether or not the vehicle speed calculated based on the vehicle speed exceeds the violation speed; and if the vehicle speed exceeds the violation speed by the time difference / speed determination unit, the extracted Doppler The difference between the Doppler velocity calculation unit that obtains and averages the Doppler velocity of the vehicle for the two radio waves based on the frequency component and the difference between the Doppler velocity of the vehicle by the two radio beams obtained by the topler velocity calculation unit is a predetermined value. When it is larger than the above, it is determined that the vehicle is meandering instead of going straight, and a meandering / speed calculating unit that calculates the meandering speed of the vehicle is provided.

The code sequence generation speed of the code generator may be changed to adjust the distance width of the gate through which the vehicle passes. Further, the delay time of the bit delay unit may be changed to adjust the distance to the gate through which the vehicle passes. You may make it specify the distance width of the gate which a vehicle passes with respect to each of several lanes, and may specify the distance to a gate.

According to the vehicle speed detecting apparatus of the present invention, by using the spread spectrum as the modulation of the radio wave beam, even if the carrier waves of the two antennas are the same, the respective signals can be separated without interference. Become. A code sequence for specifying the distance width of the gate through which the vehicle passes based on the time when the peak value obtained by despreading the demodulated signals of the received signals by the two antennas, and for causing the correlator to despread By delaying by a certain number of bits and specifying the distance from the two antennas to the gate through which the vehicle passes, the effect of multipath is eliminated and each vehicle can be separated easily. By extracting only the Doppler frequency component from the output of the correlator, the Doppler signals other than those of the vehicle are attenuated, so that the effects of snowfall and rainfall can be removed. Only when the speed of the vehicle exceeds the speed of violation by the time difference / speed determination unit, unnecessary signals are obtained by calculating and averaging the Doppler speeds of the two radio waves based on the extracted Doppler frequency components. It is not necessary to perform processing, and statistical accuracy is improved. If it is determined that the vehicle is meandering instead of going straight, the meandering speed of the vehicle is calculated, which further improves the accuracy.

Further, the code sequence generation speed of the code generator is changed to adjust the distance width of the gate through which the vehicle passes, or the delay time of the bit delay unit is changed to the gate through which the vehicle passes. By adjusting the distance, it becomes possible to cope with the installation situation of the vehicle speed detection device on the road. Further, by specifying the distance width of the gate through which the vehicle passes for each of the plurality of lanes and specifying the distance to the gate, it is possible to handle a plurality of lanes.

[0009]

BEST MODE FOR CARRYING OUT THE INVENTION Embodiments of the present invention will be described below with reference to the drawings. FIG. 1 is a view showing the external appearance of a vehicle speed detecting device according to the present invention, which is fixed or movable for expropriation. This vehicle speed detection device uses, for example, a millimeter wave spread spectrum system to radiate two kinds of spread spectrum radio waves by shifting their directions, and calculates the speed of the vehicle from each Doppler signal obtained by despreading the reflected signal. It is to be calculated. The speed measurement range is 40 to 300 km / h, and the measurement distance is 3 to 100 m.

This vehicle speed detecting device has, for example, a stationary type and a moving type, and both shapes are about 300 × about 300 × about 200 (mm ³ ), and the weight thereof is about 3 kg or less, It will be installed on the shoulder of highways and general roads. Therefore, since the main body is small and lightweight, stable setting is possible.
The installation conditions are, for example, that the height position of the road shoulder is 5 to 6 m to capture an image of 30 to 45 m on the road, and the beam width of the antenna of the vehicle speed detection device is AZIMUTH: 2 °, ELEVAT.
ION: Try to be in the range of 20 °. Further, the transmission signal power can be realized with 10 mw ± 10%.

The transmission signal has a frequency of 60 GHz (wavelength of about 5 m
If m) is used, size reduction and improvement of resolution can be achieved. Therefore, the weather resistance can be ensured as follows. First, the effect of rainfall will be explained. 50 m on the road (10 round trips)
The theoretical value of the attenuation of transmitted and received radio waves due to rainfall in the case of 0 m) is roughly as shown in the table below.

[0012]

[Table 1]

As shown in this table, the attenuation due to rainfall is almost negligible. Next, the influence of rainfall rate and snow rate will be described. Some of the above-mentioned attenuation amounts are due to absorption and reflection of radio waves, but the main cause of the attenuation is absorption rather than reflection due to rainfall or snowfall. Therefore, the Doppler signal reflected and received by rainfall or snowfall is considerably weaker in level than the reflection from the vehicle. Further, since the Doppler signals from vehicles other than the relative speed of 40 to 300 km / h are further attenuated by the filter in the signal processing process described later, the influence of rainfall as well as snow is almost eliminated.

Next, regarding the environment, especially regarding smoke,
The radio wave used has a frequency of 60 GHz and a wavelength of about 5 mm. On the other hand, smoke particles are very small, so that the problem of smoke pollution can be dealt with. Also, especially regarding salt damage, the antenna surface used in this vehicle speed detection device is protected by a radome of Teflon material, its signal processing board is subjected to moistureproof processing, and its housing is made of a material that does not progress corrosion such as aluminum. To use. Therefore, the problem of salt damage can be dealt with.

FIG. 2 is a diagram for explaining the configuration of the vehicle speed detecting device according to the embodiment of the present invention. As shown in the figure, antennas 1 and 2 which transmit radio waves (beams 1 and 2) toward a target object and receive reflected waves of the target object, which are in a relationship of a constant angle with respect to the vehicle, A signal processing unit 3 or 4 connected to each antenna 1 or 2 to form a signal for a transmission wave and processing a reception wave as a signal, and a carrier signal f0 for common use by the signal processing units 3 and 4. An oscillator 5 for generating (= 60 GHz), a directional coupler 6 for distributing an output signal of the oscillator 5 to the signal processing units 3 and 4, and a directional coupler 6
And the speed calculator 9 for obtaining the speed of the vehicle on the basis of the processing results of the signal processors 3 and 4. And. Since the signal processing units 3 and 4 have the same configuration,
The signal processing unit 3 will be described below.

The signal processing section 3 includes a circulator 31 connected to the antenna 1 and a modulator 32 which directly spread-modulates one output of the distributor 7 and outputs it to the circulator 31.
, A demodulator 33 that mixes the output of the circulator 31 with the other output of the distributor 7 to form an intermediate frequency IF, an amplifier 34 that amplifies the output signal of the demodulator 33, and an amplified signal from the amplifier 34. A correlator 35 that forms a gate width of a range gate that allows a vehicle to pass by performing correlation and despreading with a digital code sequence of a code generator 37 described later.
A Doppler filter / amplifier 36 for extracting and amplifying only a predetermined frequency component of the output signal components of the correlator 35, that is, a Doppler frequency component included in a signal that travels back and forth on a path to a target object; A digital code sequence having a high bit rate in order to cause 32 to perform direct spread modulation and to cause correlator 35 to perform despreading,
For example, a code generator 37 for generating an M-sequence code and an output code of the code generator 37 between the code generator 37 and the correlator 35 are delayed by, for example, 2 bits, and cooperate with the correlator 35. And a bit delay unit 38 for forming the gate distance of the distance gate.

Here, the digital code sequences of the code generators 37 and 47 (not shown) in the signal processing units 3 and 4 are made different. Next, the distance gate by the bit delay unit 38 and the correlator 35 will be described in detail. When a direct diffusion modulated radio wave is emitted and reflected from a target object such as a vehicle, the reflected wave has a time difference corresponding to the propagation distance of the radio wave back and forth to the vehicle. what if,
When the M-sequence code is used as the direct spread modulation signal, the correlation output of the two codes exhibits a peak value when the time difference is 0 (that is, the phase difference is 0), and the correlation output also decreases with an increase in the phase difference, and 1 clock If it deviates by (1 bit) or more, almost no correlation output can be obtained. The correlator 35 will have a temporal gate width of ± 1 bit. For the principle of the correlation of the spread modulation signal, see the document “SPREAD SPE
CTRUM SYSTEM, written by RCDIXON ”.

As a result, when the direct diffusion modulated signal contained in the reflected wave signal is correlated with another direct diffusion modulated signal which has been delayed by a time corresponding to the propagation distance in advance, the phase difference is obtained. Is 0, the correlation output has a peak value. Specifically, the intermediate frequency signal generated by the demodulator 35 has the same code as that of the modulated transmission signal and has a phase corresponding to the propagation distance in advance, that is, the phase is set by the bit delay unit 38. If you take the correlation with the delayed code,
The correlation output of the signal propagated through the preset propagation distance has a peak, but at other propagation distances, the correlation distance is hardly obtained.

In this way, it is possible to set the gate width of the distance from the temporal gate width of the correlator 35, and to set the gate distance from the propagation distance to the correlator 35 to the gate. FIG. 3 is a diagram illustrating a distance gate.
As shown in this figure, the distance from the antennas 1 and 2 to the vehicle is the gate distance, and the width through which the vehicle passes is the gate width. The code bit rate of the code generator 37 is, for example, 50
Assuming Mbps, the gate distance E is: gate distance E = 1/2 {4 bits / (50 × 10 ⁶ bp) in consideration of round-trip propagation time.
s)} × 3 × 10 ⁸ m / s = 12 m The gate width F is: gate width F = 1/2 {2 bits / (50 × 10 ⁶ bp
s)} × 3 × 10 ⁸ m / s = 6 m.

Therefore, the gate width is determined by the code generator 37.
It can be adjusted by changing the sign bit rate of.
Further, the gate distance can be adjusted by changing the bit delay of the bit delay unit 38. FIG. 4 is a diagram showing an example of measuring the speed of a vehicle using a distance gate. As shown in the figure, the distance gates are provided in the lanes where the vehicles of beam 1 and beam 2 travel, and the vehicle passes the distance gate of beam 1 and then the distance gate of beam 2. In this way, the speed of only the vehicle passing through the distance gate is calculated as described later. In this way, the speed of the vehicle is measured using the distance gate, so that there is no interference or interference due to the influence of multipath, and the vehicles can be separated easily. That is, the reflection signal from the vehicle traveling outside the distance gate can be removed. Further, since it is possible to remove a reflected signal from a building or the like outside the range gate, the resistance to interference with unnecessary radio waves in the operating environment is improved.

Further, the transmission signals from the respective antennas 1 and 2 are spectrum-spread by different direct-spread modulation signals, and the reception signal from the target is despread with the same code used for transmission. Despite being the same, each signal can be separated without interference. FIG. 5 is a diagram for explaining the speed calculator 9 in FIG.
As shown in the figure, the speed calculation unit 9 inputs signals from the Doppler filter and amplifier 36 of the signal processing unit 3 and the Doppler filter and amplifier 46 (not shown) of the signal processing unit 4 so that the vehicle receives between two beams. The time difference / speed determination unit 91 that calculates the speed V of the vehicle from the time difference ΔT that passes through and determines the speed violation, and similarly the speed calculation unit 9 includes the Doppler filter and amplifier 36 of the signal processing unit 3 and the signal processing unit 4 The signal from the Doppler filter and the amplifier 46 of No. 1 is input and the velocity Vd is obtained from the Doppler frequencies of the beam 1 and the beam 2.
And a meandering / speed calculating section 93 for calculating the speed Va at the time of meandering of the vehicle based on the Doppler frequency obtained by the Doppler / speed calculating section 92.

FIG. 6 is a diagram for explaining the time difference / speed calculation unit 91 in FIG. 5, FIG. 7 is a diagram for explaining the symbols used for speed calculation, and FIG. 8 is a signal waveform in the time difference / speed calculation unit 91. FIG. As shown in FIG. 6, the diodes 911 and 912 of the time difference / velocity calculator 91 extract signals from the Doppler filters and amplifiers 36 and 46 for the beam 1 and the beam 2 (see FIGS. 8C and 8D).
Rectify. The averaging circuits 913 and 913 average the rectified signals. When the averaged signals exceed a predetermined level at times t2 and t4, the comparator circuits 915 and 916 change their output signals from "L (low)" to "H (high)".
When it is changed to a signal and falls below a predetermined level at t3 and t5, the output signal is changed from the “L” signal to the “H” signal (see FIGS. 8A and 8B). Timer 917
From the “L (low)” signal of the comparison circuit 915 to “H (hig
h) ”signal is started and the comparison circuit 916 starts.
Of the vehicle passing through beam 1 and beam 2 after being stopped by the change from the "L" signal to the "H" signal of
(= T4-t2) is calculated. When the distance between the beam 1 and the beam 2 at the distance gate through which the vehicle passes is L (see FIG. 7), the speed determination unit 918 calculates the speed V of the vehicle as V = L / ΔT. Then, it is determined whether the vehicle speed exceeds the violation speed V0.

FIG. 9 illustrates the Doppler / speed calculator 92. As shown in the figure, the Doppler / speed calculation unit 92 includes a switch 921 for permitting and prohibiting the input of signals from the Doppler filter and amplifier 36 of the signal processing unit 3 and the Doppler filter and amplifier 46 of the signal processing unit 4. , 922 and A / D converters 923, 924 (Analog to Digital) connected to the switches 921, 922.
Converter) and FFTs 925 and 926 (Fast Fourier Tran) for obtaining frequencies fd1 and fd2 of the digital Doppler signals relating to the beam 1 and the beam 2 by frequency analysis.
sformation) and speed calculators 927 and 928 for calculating speeds Vd1 and Vd2 from the frequencies fd1 and fd2.
And the speeds Vd1 and Vd2 are averaged to obtain Vd = (Vd1
Averaging unit 929 for calculating + Vd2) / 2 and speed Vd
The difference determination unit 930 that determines the difference ΔVd = | Vd1−Vd2 | between 1 and Vd2 and determines that this difference is larger than the predetermined value A.
If the difference output of the difference unit 930 is small, the averaging unit 92
A switch 9 that permits the average output of the speed of 9 and prohibits the average output of the speed of the averaging unit 929 when the difference output is large.
31 and a switch 932 for permitting and prohibiting output.

Here, the speed calculators 927 and 928 calculate the speeds Vd1 and Vd2 as follows. Vd1 = λ · fd1 / (2cos θ1) Vd2 = λ · fd2 / (2cos θ2) λ = wavelength of carrier wave f0 When the difference output of the difference unit 930 is small, the vehicle is traveling straight and the vehicle is beam 1 and beam 2. Means that the average speed Vd is equal, and in this case the average speed Vd is calculated as follows: Vd = (Vd1 + Vd2) / 2, and this averaging improves the statistical accuracy. On the other hand, when the difference output of the difference unit 930 is large, it is considered that the vehicle is deviating from going straight and performing meandering operation.
In the case of the meandering operation, an error occurs in the Doppler speed on the assumption that the vehicle is going straight. Therefore, the speed Va during the meandering operation is calculated as follows.

FIG. 10 is a diagram for explaining the calculation of the speed Va by the meandering / speed calculating section 93. As shown in FIG.
When Δθ = θ2−θ1 is set, ρ is an entry angle when meandering with respect to a straight ahead, and Va is a vehicle speed, fd1 = (2Va / λ) · cos (θ1−Δθ + ρ) = (2Va / λ) · { cos (θ1 + ρ) cosΔθ− sin (θ1 + ρ) sinΔθ} fd2 = (2Va / λ) · cos (θ1 + Δθ + ρ) = (2Va / λ) {cos (θ1 + ρ) cosΔθ + sin (θ1 + ρ) sinΔθ} (θ) + ρ ) = (Λ / 4 Vacos Δθ) · (f
d1 + fd2) sin (θ1 + ρ) = (λ / 4 Vasin Δθ) · (f
d1-fd2) is calculated.

Cos (θ1 + ρ) ² + sin (θ1 +
ρ) ² = 1 and Va = (λ / 2) · [{(fd1 + fd2) / cos Δ
θ} ² + {(fd1-fd2) / sin Δθ} ² ] is obtained. The accuracy is further improved by the speed Va considering the meandering. FIG. 11 is a diagram for explaining a series of operations of the speed calculator 9.

In step S1, the velocity V due to the two-beam transit time difference is calculated. In step S2, it is judged based on the speed V whether or not the vehicle exceeds the violation speed. If the judgment is "NO" and the speed is not exceeded, the process proceeds to the end step, and if "YES", the process proceeds to step S3. In step S3, the precise velocity Vd based on the two-beam Doppler frequency is set only when the violating velocity is exceeded in step S2.
Is calculated. Therefore, it becomes unnecessary to perform unnecessary signal processing.

In step S4, it is determined from the respective velocities V1 and V2 of the two beams in step S3 whether or not | V1−V2 | ≧ A holds. Here, A is, for example, 10
km / h. If this determination is "NO", the speed Vd is output and the process proceeds to the end step, and if "YES", the process proceeds to step S5.

In step S5, if there is a significant difference between the velocities V1 and V2 of the two beams, the meandering velocity Va is calculated and output. FIG. 12 is a diagram illustrating a configuration of a vehicle speed detection device according to another embodiment of the present invention, and FIG. 13 is a diagram illustrating an example of measuring a vehicle speed using the distance gate in the configuration of FIG. Is. As shown in FIG. 12, a correlator 35 is newly provided with a correlator 51, and each of the correlators 35 and 51 is provided with a 4 delay unit 38 and a new 6 delay unit 50. By providing two distance gates in this way, it becomes possible to cope with two lanes as shown in FIG.

FIG. 14 is a diagram showing the relationship between the gate distance and the gate width of the range gate, and FIG. 15 is the output level A of the range gate and the Doppler filter and amplifiers 36 and 52.
It is a figure which shows the relationship with 1, A2 (B1, B2). FIG.
4, the distance gate width F for the beams 1 and 2
As is, the two gate distances E1 and E2 are as follows.

Gate distance E1 = 1/2 {4 bits / (5
0 × 10 ⁶ bps)} × 3 × 10 ⁸ m / s = 12 m Gate distance E2 = 1/2 {6 bits / (50 × 10 ⁶ b)
ps)} × 3 × 10 ⁸ m / s = 18 m As shown in FIG. 15, the output levels A1 and A2 are generated in the Doppler filter and amplifiers 36 and 52 only when the vehicle passes the range gate.

FIG. 16 is a diagram for explaining the structure of a vehicle speed detecting device according to another embodiment of the present invention. As shown in the figure, a correlator 53, a Doppler filter / amplifier 54, and an 8-bit delay unit 55 are further provided, and the same can be applied to three lanes. The gate distance E3 is as follows: gate distance E3 = 1/2 {8 bits / (50 × 10 ⁶ b
ps)} × 3 × 10 ⁸ m / s = 24 m.

[0033]

As described above, according to the present invention, since spread spectrum is used as the modulation of the radio wave beam,
Even if the carrier waves of the two antennas are the same, it is possible to separate the respective signals without interference. Based on the reflected signal from the vehicle obtained by despreading the demodulated signals of the received signals by the two antennas, the distance width of the gate that the vehicle passes through is specified, and the code sequence for the correlator to despread Since the distance from the two antennas to the gate through which the vehicle passes is specified with a fixed delay, the effects of multipath are eliminated and each vehicle is easily separated. Since only the Doppler frequency component is extracted from the output of the correlator, the Doppler signals other than those of the vehicle are attenuated, and the effects of snowfall and rainfall can be removed. Only when the vehicle speed exceeds the violation speed by the time difference / speed determination unit, the vehicle Doppler speeds of the two radio waves are calculated based on the extracted Doppler frequency components and averaged, so unnecessary signal processing is performed. There is no need to do it and statistical accuracy improves. If it is determined that the vehicle is meandering instead of going straight, the meandering speed of the vehicle is calculated, which further improves the accuracy. Since the code sequence generation speed of the code generator is changed to adjust the distance width of the gate through which the vehicle passes, and the delay time of the bit delay unit is adjusted to adjust the distance to the gate through which the vehicle passes. It becomes possible to cope with the installation situation of the speed detection device on the road. Since the distance width of the gate through which the vehicle passes is specified for each of the plurality of lanes and the distance to the gate is specified, it is possible to handle a plurality of lanes.

[Brief description of drawings]

FIG. 1 is a diagram showing an external appearance of a vehicle speed detection device according to the present invention, which is fixed or movable for expropriation.

FIG. 2 is a diagram illustrating a configuration of a vehicle speed detection device according to an embodiment of the present invention.

FIG. 3 is a diagram illustrating a distance gate.

FIG. 4 is a diagram showing an example of measuring a vehicle speed using a distance gate.

5 is a diagram illustrating a speed calculation unit 9 of FIG.

6 is a diagram illustrating a time difference / speed calculation unit 91 in FIG.

FIG. 7 is a diagram illustrating symbols used for velocity calculation.

FIG. 8 is a diagram showing a signal waveform in the time difference / speed calculation unit 91.

9 is a diagram illustrating a Doppler / velocity calculation unit 92. FIG.

FIG. 10 is a diagram for explaining calculation of a speed Va by a meandering / speed calculating unit 93.

FIG. 11 is a diagram illustrating a series of operations of the speed calculator 9.

FIG. 12 is a diagram illustrating a configuration of a vehicle speed detection device according to another embodiment of the present invention.

13 is a diagram showing an example of measuring the speed of a vehicle using the distance gate in the configuration of FIG.

FIG. 14 is a diagram showing a relationship between a gate distance and a gate width of a distance gate.

FIG. 15 is a diagram showing the relationship between the distance gate and the output levels A1, A2 (B1, B2) of the Doppler filter and amplifiers 36, 52.

FIG. 16 is a diagram illustrating a configuration of a vehicle speed detection device according to another embodiment of the present invention.

[Explanation of symbols]

 1, 2 ... Antenna 35 ... Correlator 36 ... Doppler filter and amplifier 37 ... Code generator 38 ... Bit delay unit 91 ... Time difference / speed determination unit 92 ... Doppler / speed calculation unit 93 ... Meandering / speed calculation unit

─────────────────────────────────────────────────── ─── Continuation of the front page (51) Int.Cl. ⁶ Identification code Internal reference number FI Technical indication G01S 13/53 G01S 13/53

Claims (4)

[Claims] 1. A vehicle speed detecting device for reflecting a radio wave to a vehicle traveling straight ahead and detecting the speed of the vehicle on the basis of reflection information, wherein two radio wave beams are emitted by spectrally spreading the spectrum at a constant angle. Two antennas to receive, a correlator to specify the distance width of the gate through which the vehicle passes based on the time when the peak value obtained by despreading the demodulated signals of the signals received by the two antennas, and spread spectrum A code generator that generates a code sequence at a constant speed to perform despreading, and a code sequence for the despreading performed by the correlator to delay two bits from the two antennas to the gate through which the vehicle passes. , A bit delay unit that specifies the distance of, a Doppler filter and an amplifier that extract only Doppler frequency components from the output of the correlator, and the extracted Doppler frequency Based on the levels of several components, the time difference between the passage gates of the vehicle formed by the two radio waves is calculated, and it is determined whether the calculated vehicle speed exceeds the violation speed based on this time difference. When the vehicle speed exceeds the violation speed by the time difference / speed determination unit and the time difference / speed determination unit, the Doppler speeds of the two radio waves are calculated based on the extracted Doppler frequency components and averaged. When the difference between the Doppler speed calculation unit and the Doppler speed of the vehicle due to the two radio beams obtained by the topler speed calculation unit is larger than a predetermined value, the vehicle meanders instead of going straight. A vehicle speed detecting device, comprising: a meandering / speed calculating unit that determines that the vehicle is meandering speed. 2. The vehicle speed detecting device according to claim 1, wherein a code sequence generation speed of the code generator is changed to adjust a distance width of a gate through which the vehicle passes. 3. The vehicle speed detecting device according to claim 1, wherein a delay time of the bit delay unit is changed to adjust a distance to a gate through which the vehicle passes. 4. The vehicle speed detecting device according to claim 1, wherein a distance width of a gate through which a vehicle passes is specified for each of a plurality of lanes, and a distance to the gate is specified.