JP3354199B2 - Speed measuring device - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION This invention relates to an improvement of the speed apparatus for measuring the running speed of an automobile by utilizing a de Ppura effect.

[0002]

2. Description of the Related Art A speed measuring device for measuring a running speed of an automobile or the like using the Doppler effect of radio waves is used for measuring a traffic flow, controlling a traffic violation, and the like. , As shown in FIG. In the figure, 1 is a traveling vehicle as an object to be measured, 2 is a gun oscillator as a radio wave source, 3 is a circulator, 4 is a radio wave from the gun oscillator 2 radiated to the traveling vehicle 1 as a transmission wave 4, and An antenna for receiving the received wave 6 from 1;
Is an injection wave 7 injected through the circulator 3 from the gun oscillator 2 and a reception wave 6 obtained through the antenna 4
Is input and the transmission wave 5 is obtained by mixing the two frequencies.
Detector for obtaining a Doppler signal 9 having a frequency component equal to the difference frequency between the received wave number 6 and the received wave number 10, an amplifier 10 for amplifying the amplitude of the Doppler signal 9, and an amplifier 11 for the amplifier 10.
The counting circuit converts the frequency of the Doppler signal amplified by the counting into the speed of the traveling vehicle 1 by counting. The circulator 3 is configured so that radio waves entering from the first terminal 31 are guided to the second terminal 32 and radio waves entering from the second terminal 32 are guided to the third terminal 33. A part of the radio wave from
Is also output to the terminal 33 of.

[0003] The conventional speed measuring apparatus is configured as described above, and the transmitted wave 5 hitting the traveling vehicle 1 is reflected and input as a received wave 6 to the mixed detector 8 via the path from the antenna 4 to the circulator 3. The mixed detector 8 extracts a mixed detection output 9 by frequency mixing of the reception wave 6 and the injection wave 7. At this time, according to the Doppler effect, the following equation is established between the speed V of the traveling vehicle 1 and the frequency f _d of the mixed detection output 9. V = c × f _d / (2 × f _o ) (1) where f _o is the frequency of the transmitted wave 5 c is the propagation speed of the radio wave

[0004] The counting circuit 11 measures the frequency of the mixed detection output 9 amplified by the amplifier 10 and measures the speed of the traveling vehicle 1 according to the equation (1). On the other hand, the power p _{r of the} received wave received by the antenna 4 is represented by the following equation. ^{_{pr αp t × σ / R 4}} (2) where p _t is the distance of the traveling vehicle 1 and the RCS R antenna 4 of the transmission power sigma of the transmission wave 5 vehicle 1

That is, the strength of the received wave is proportional to the radar reflection cross-sectional area of the traveling vehicle 1 and inversely proportional to the fourth power of the distance between the antenna 4 and the traveling vehicle 1. In the configuration of FIG. 7, the minimum received power p _{min at} which the speed can be measured is determined by the S / N ratio (signal to noise ratio) of the mixed detector 8 and the amplifier 10, and the received power p
_{When r} ≧ p _min , the speed of the traveling vehicle 1 can be measured, and when received power p _r <p _min , the speed cannot be measured.

Equation (2) shows that the distance at which the speed can be measured is determined by the radar reflection cross-sectional area σ of the traveling vehicle. On the other hand, the radar reflection cross-sectional area σ is determined by the shape of the traveling vehicle 1, and a general passenger vehicle is generally smaller than a large vehicle such as a truck.
Therefore, the measurable distance differs depending on the vehicle type. In the case of this phenomenon , it may be difficult to specify which vehicle has been measured in the measurement on the road for a plurality of vehicles.

SUMMARY OF THE INVENTION The present invention has been made to solve the above problems, and provides a speed measuring device which electronically limits a measurable range and reduces a change in a measurable range depending on a vehicle type. With the goal.

[0008]

SUMMARY OF THE INVENTION A speed measuring apparatus according to the present invention includes a pulse generator, a frequency divider, a modulator, and two sample-and-hold circuits, and is within a fixed distance from an antenna. The speed of only the traveling vehicle can be measured.

[0009]

According to the present invention, there is no transmission wave in the transmission area.
Other vehicles in front of the antenna from the specified area
If the vehicle exists, the vehicle
The speed is not measured even if the vehicle is within
This is an effective means for detecting speeding vehicles. Ma
In addition, since the upper limit distance and the lower limit distance from the antenna whose transmission wave is subjected to rectangular wave modulation and whose speed can be measured by the sample-and-hold circuit can be determined, the upper limit is almost independent of the radar reflection cross section of the vehicle. The distance and the speed of only the vehicle within the above lower limit distance can be measured. Furthermore, speed
Violating vehicles can be tracked from captured images
it can.

[0010]

【Example】

Embodiment 1 FIG. FIG. 1 is a configuration diagram of Embodiment 1 of the present invention. In the drawing, reference numeral 20 denotes a pulse generator, 21 denotes a modulation pulse 22 based on an output from the pulse generator 20, an upper limit distance sample pulse 23, Lower limit distance sample pulse 24
A frequency divider 25 that outputs a pulse signal from the gun oscillator 25 by a modulation pulse 22;
Is an upper limit distance sample and hold circuit that samples and holds the detection output 9 from the mixing detector 8 with the upper limit distance sample pulse 23 and outputs an upper limit Doppler signal 42;
Reference numeral 41 denotes a lower-limit distance sample-and-hold circuit that samples and holds the detection output 9 from the mixing detector 8 using a lower-limit distance sample pulse 24 and outputs a lower-limit Doppler signal 43. 44 amplifies the upper-limit Doppler signal 42 and outputs an upper-limit pulse 46. The upper limit distance signal amplifier, 45, which amplifies the lower limit Doppler signal 43 and outputs the lower limit pulse 47, counts the frequency of the lower limit pulse 47, and exceeds a predetermined value. In this case, the lower limit pulse counter 12 that outputs the count prohibition signal 49 gates the upper limit pulse 46 by the count prohibition signal 49, and outputs the upper limit pulse 46 to the counting circuit 11 only when the count prohibition signal 49 is not output. Is a gate that acts on
2, 3 and 4 are diagrams for explaining the operation of each unit in FIG.

Next, the operation of the speed measuring device according to the present invention will be described. In the velocity measuring device configured as described above, the transmitted wave 5 hitting the traveling vehicle 1 is reflected and input as a received wave 6 to the mixing detector 8 via the path from the antenna 4 to the circulator 3. The mixed detector 8 extracts a mixed detection output 9 by frequency mixing of the reception wave 6 and the injection wave 7. Incidentally, the transmission wave 5 is modulated into a rectangular wave by the modulation pulse 22.

The situation of the mixed detection output in this case will be described with reference to FIGS. 2, 3 and 4. FIG. FIG. 2 shows that the modulation pulse has a pulse width T.
w, the repetition time width Tr, and the transmission wave 5
Are also square-wave modulated as shown in FIG. On the other hand, the received wave 6 is received with a delay time Td depending on the distance R between the antenna 4 and the traveling vehicle 1. The delay time Td is given by the following equation. Td = 2 × R / c (3) where c is the propagation speed of the radio wave

The mixed detector 8 receives the injection wave 7, that is, both the transmission wave 5 and the reception wave 6, so that the mixed detection output 9 is output only when Td <Tw. In other words, the mixed detection output 9 is generated when the distance between the traveling vehicle 1 and the antenna 4 is within Tw × c / 2. If the duty ratio Tw / Tr is selected to be, for example, about six times or more, the actual received power Pr
Is represented by the following equation. _pr∝ ｛ _pt × σ / R ⁴ ｝ × Td / Tr (4) where R <Tw × c / 2 _pr = 0 (5) where R ≧ Tw × c / 2

That is, the Doppler signal of the vehicle can be obtained only when the vehicle is within a predetermined distance by the rectangular wave modulation.

FIG. 3 illustrates that the function of limiting the distance is added by the operation of the sample and hold circuit.
In the configuration of FIG. 1, two types of sample and hold circuits, an upper limit distance sample and hold circuit 40 and a lower limit distance sample and hold circuit 41, are prepared, and are operated by the upper limit distance sample pulse 23 and the lower limit sample pulse 24, respectively. . Specifically, as shown in FIG. 3, the detector output 9 during the ON period of the sample pulse is captured. On the other hand, in FIG. 3, the positions of the upper limit distance sample pulse 23 and the lower limit distance sample pulse 24 are Tu = 2 × Ru / c (6) Tl = 2 × R1 / c (7)

Where Ru is the upper limit distance, Rl
Is the lower limit distance. Note that Tu <Tw, Tl <Tw, T
l <Tu. With this configuration, the upper limit Doppler signal 42 from the upper limit distance sample hold circuit 40 is output only when the distance of the traveling vehicle 1 from the antenna 4 is within Ru. Further, the lower limit Doppler signal 43 from the lower limit distance sample hold circuit 41 is output only when the distance of the traveling vehicle 1 from the antenna 4 is within Rl. FIG. 4 shows this relationship.

In FIG. 1, a lower limit Doppler signal 43 is amplified by a lower limit distance signal amplifier 45 and supplied to a lower limit pulse counter 48 as a lower limit pulse 47. The lower limit pulse counter 48 counts the frequency of the lower limit pulse 47, and when the frequency exceeds a predetermined value, outputs a count prohibition signal 49 to the gate 9.
Output to Here, the predetermined value is lower limit pulse 4
7, the influence of noise is considered, and basically, the presence or absence of the lower limit pulse 47 may be detected. That is, when the lower limit pulse 47 is output, the count inhibition signal 49 is output. At the gate 9, the count inhibition signal 49 changes to the upper limit pulse 46.
And supplies the upper limit pulse 46 to the counting circuit 11 only when there is no counting prohibition signal 49. In FIG. 4, only when the traveling vehicle is between the upper limit distance Ru and the lower limit distance Rl, that is, when Tu · c / 2> R ≧ T1 · c / 2 is satisfied, the upper limit pulse 46 is counted by the counting circuit 11.
And a speed measurement is performed.

FIG. 5 shows the position at which the speed is measured. FIG. 5 is a side view of the road, and shows a situation in which the antenna 4 is installed on the road by columns or the like, and radio waves are emitted obliquely downward toward the road surface. As described above, the region where the speed can be measured is such that the distance from the antenna 4 is between the upper limit distance Ru and the lower limit distance Rl, and the region is limited. Therefore, regardless of the spread of the radio wave beam, the measurable region is limited, so that the target vehicle can be specified. The above function works effectively even when a plurality of vehicles are running on the road. That is, when another vehicle or the like exists before the lower limit distance Rl, the speed is not measured even if the vehicle is between the upper limit distance Ru and the lower limit distance Rl. This is extremely effective for identifying a vehicle, and is particularly effective for detecting a speeding vehicle.

FIG. 6 is a block diagram of another embodiment of the present invention. In FIG. 6, reference numeral 14 denotes a measured speed value of the traveling vehicle 1 which is an output of the counting circuit 11, and reference numeral 15 denotes a speed limit for setting a speed limit 16. The setting switch 17 compares the measured speed value 14 with the speed limit 16 and, when the measured speed value 14 exceeds the speed limit 16, outputs the photographing command signal 18 with the traveling vehicle 1 as a speeding vehicle. The speed comparator 19 has a built-in shutter and is a camera for photographing a running vehicle as a still image.

Next, the operation of the speed measuring apparatus according to the present invention will be described with reference to FIG. In the speed measuring device configured as described above, the transmission wave 5 hitting the traveling vehicle 1 is reflected and input as a reception wave 6 to the mixing detector 8 via the route from the antenna 4 to the circulator 3, and the traveling vehicle 1 The speed measurement is performed while the antenna is located between the upper limit position Ru and the lower limit position Rl from the antenna, and the measured value is a speed measurement value 14 as an output of the counting circuit 11. On the other hand, the speed limit switch 16 is set to a speed limit 16 for determining a speed violation. The speed comparator 17 compares the measured speed value 14 with the speed limit 16 and outputs a photographing command signal 18 when the measured speed value 14 exceeds the speed limit 16 to release the shutter of the camera 19. Activated, the traveling vehicle 1 is photographed as a speeding vehicle. This camera 19 is the traveling vehicle 1
Is photographed, and related data such as a speed measurement value is printed on the screen as data indicating a speed violation fact.

The speed violation can be tracked from the image taken by the camera 19 in this manner. In particular, since the speed measurement area is limited between the upper limit distance Ru and the lower limit distance Rl, it is effective for specifying the vehicle.

[0022]

As described above, the present invention is extremely effective in specifying a target vehicle because the speed measurement area can be limited regardless of the radar reflection area of the running vehicle. Also, by performing signal processing of the speed measuring means, it is detected that another vehicle is present in front of the speed measuring means as viewed from the antenna with respect to a predetermined area in the transmission area of the transmission wave.
In such a case, since the speed is not measured even if the vehicle is in a predetermined area, it is extremely effective for specifying the vehicle, and is particularly effective for detecting a speeding vehicle. Furthermore, since the image of the speeding vehicle can be taken and the speed measurement area is limited, it is effective for specifying the vehicle in violation.

[Brief description of the drawings]

FIG. 1 is a configuration diagram of a speed measuring device according to Embodiment 1 of the present invention.

FIG. 2 is a diagram showing the operation of the first and second embodiments of the present invention.

FIG. 3 is a diagram showing the operation of the first and second embodiments of the present invention.

FIG. 4 is a diagram showing the operation of the first and second embodiments of the present invention.

FIG. 5 is a diagram showing the operation of the first and second embodiments of the present invention.

FIG. 6 is a configuration diagram of a speed measuring device according to a second embodiment of the present invention.

FIG. 7 is a configuration diagram of a conventional speed measuring device.

[Explanation of symbols]

 REFERENCE SIGNS LIST 1 traveling vehicle 2 gun oscillator 3 circulator 4 antenna 5 transmission wave 6 reception wave 7 injection wave 8 mixing detector 9 mixing detection output 10 amplifier 11 counting circuit 12 gate 13 count inhibition signal 14 speed measurement value 15 speed limit setting switch 16 speed limit Reference Signs List 17 speed comparator 18 shooting command signal 19 camera 20 pulse generator 21 frequency divider 22 modulation pulse 23 upper limit distance sample pulse 24 lower limit distance sample pulse 25 modulator 31 first terminal 32 second terminal 33 third terminal 40 Upper limit sample hold circuit 41 Lower limit sample hold circuit 42 Upper Doppler signal 43 Lower Doppler signal 44 Upper limit signal amplifier 45 Lower limit signal amplifier 46 Upper pulse 47 Lower pulse 48 Lower pulse counter 49 Count inhibit signal

Claims (4)

(57) [Claims] 1. A speed measuring device for transmitting and receiving a transmission wave obliquely downward toward a road on which a plurality of traveling vehicles pass and receiving reflected waves from the traveling vehicle, and measuring a speed of the traveling vehicle. A speed measuring means for measuring a speed based on a Doppler signal of a reflected wave reflected from a traveling vehicle passing through a predetermined area in a transmission area of the transmission wave on the road and received by the transmission / reception means; It is detected by performing signal processing of the speed measuring means that the vehicle is present between the predetermined area and the transmitting / receiving means and at a position closer to the speed measuring means than the predetermined area.
By, speed measuring apparatus characterized by comprising a prohibiting means for prohibiting the speed measurement of the vehicle passing through the predetermined area by the speed measuring means. 2. The speed measuring device according to claim 1, further comprising photographing means for photographing the traveling vehicle having exceeded the speed based on the measured value of the traveling vehicle measured by the speed measuring means. 3. A speed measuring device for transmitting and receiving a transmission wave obliquely downward toward a road on which a plurality of traveling vehicles pass and receiving reflected waves from the traveling vehicle, and measuring a speed of the traveling vehicle. In the above, a pulse modulator for pulse-modulating the transmission wave, and a range in which the reception wave reflected from the traveling vehicle and received by the transmission / reception means overlaps the pulse width between the pulse-modulated transmission wave. A detector that obtains a frequency-mixed detection output, and has a transmission area of the transmission wave, and has a transmission / reception time of the transmission wave corresponding to a position of a predetermined upper limit distance from the transmission / reception means on the road,
An upper limit sample-hold circuit that samples and holds the detection output of the detector, and has a transmission area of the transmission radio wave, and has a predetermined transmission / reception time of the transmission radio wave corresponding to a position of a predetermined lower limit distance from the transmission / reception means on the road. A lower limit sample and hold circuit that samples and holds the detection output of the detector, a gate that normally opens and closes when a sample pulse is detected by the lower limit sample and hold circuit, and a sample and hold when the gate is open Based on the Doppler signal output from the circuit,
A speed measuring device, comprising: a counting circuit for measuring a speed of only a traveling vehicle passing through an area between the upper limit distance and the lower limit distance on a road. 4. A speed comparator for issuing an alarm signal when a speed measurement value measured by the counting circuit exceeds a predetermined set speed, and photographing means for photographing the traveling vehicle by the alarm signal. The speed measuring device according to claim 3, wherein