JPH0784036A - Speed measuring apparatus - Google Patents

Abstract

PURPOSE:To prevent influence of a frequency interference and other noise by providing a waveform deciding circuit having a duty deciding circuit and an interval deciding circuit. CONSTITUTION:A transmitted wave 5 emitted to a traveling vehicle 1 is reflected and input to a mixing detector 8 through a route of an antenna 4 and a circulator 3. The detector 8 frequency-mixes a received wave 6 and an injected wave 7 to extract a Doppler signal 9, amplifies it and outputs a rectangular Doppler signal 12. The signal 12 is supplied to a duty deciding circuit 41 and an interval deciding circuit 43 to approve a Doppler waveform. An AND circuit 46 outputs a waveform decision signal 47 as an AND of a duty decision signal 42, a correlation signal 44 and a period decision signal 45. That is, the signal 47 becomes OK only when all the signals 42, 44, 45 are OK. A gate circuit 48 supplies the signal 12 to a counter 11 only when the signal 47 is OK to execute calculating of a speed.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an improvement in a speed device which measures the traveling speed of an automobile or the like by utilizing the Doppler effect of radio waves.

[0002]

2. Description of the Related Art A speed measuring device for measuring the traveling speed of an automobile or the like using the Doppler effect of radio waves is used for measuring traffic flow, controlling speed violations, etc. Is 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 transmitted wave 5, and the traveling vehicle 1 Antenna for receiving the received wave 6 from
Is input with an injection wave 7 injected from the Gunn oscillator 2 through the circulator 3 and a reception wave 6 obtained through the antenna 4, and the difference frequency between the transmission wave 5 and the reception wave 6 is obtained by mixing the frequencies of the two. A mixing detector 10 for obtaining a Doppler signal 9 as a frequency component is a Doppler signal 9
An amplifier that amplifies the amplitude of the signal of and outputs it as a rectangular wave.
Reference numeral 11 is a counting circuit that counts the frequency of the rectangular wave Doppler signal 12 amplified by the amplifier 10 and converts it into the speed of the traveling vehicle 1. Also, circulator 3
Is the radio wave entering from the first terminal 31 to the second terminal 32,
The radio wave entering from the second terminal 32 is guided to the third terminal 33, but a part of the radio wave from the first terminal is also output to the third terminal 33 as the injection wave 7. It is like this.

The conventional speed measuring device is constructed in this way, and the transmitted wave 5 hitting the traveling vehicle 1 is reflected and inputted as a received wave 6 to the mixing detector 8 via the path from the antenna 4 to the circulator 3. The mixing detector 8 extracts the Doppler signal 9 by frequency mixing the reception wave 6 and the injection wave 7. At this time, according to the Doppler effect, the traveling vehicle 1
The following equation is established between the speed V of V and the frequency f _d of the Doppler signal 9. V = c × f _d / (2 × f _o ) (1) Here, f _o is the frequency of the transmitted wave 5, c is the propagation velocity of the radio wave, and the counting circuit 11 measures the frequency of the Doppler signal 9 amplified by the amplifier 10. The speed of the traveling vehicle 1 is measured according to Equation 1.

FIG. 9 shows a case where two speed measuring devices are used close to each other. In the figure, 201 is the first speed measuring device, 202 is the second speed measuring device, f _t1 is the frequency of the transmission wave from the first speed measuring device 201, and f _r1 is the frequency from the first speed measuring device 201. The transmitted wave hits the traveling vehicle 1 and undergoes a frequency shift due to the Doppler effect, and the frequency of the reflected wave received by the first speed measuring device 201, f _t2 is the frequency of the transmitted wave from the second speed measuring device 202. , F _r2
Is the frequency of the reflected wave received by the second speed measuring device 202 after the transmission wave from the second speed measuring device 202 hits the traveling vehicle 1 and undergoes a frequency shift due to the Doppler effect. The measuring device 201 and the second speed measuring device 202 are equivalent to the speed measuring device 2 shown in FIG. In such a configuration, the first speed measuring device 201 measures the speed of the traveling vehicle 1 by frequency mixing the frequencies f _t1 and f _r1 . In addition, the second speed measuring device 202 measures the speed of the traveling vehicle 1 by frequency mixing the frequencies f _t2 and f _r2 . However, when the two speed measuring devices 201 and 202 are installed close to each other,
As shown in FIG. 9, the frequency f _t2 of the transmitted wave from the second speed measuring device 202 may be received by the first speed measuring device 201, or conversely, the first speed measuring device 20.
The frequency f _t1 of the transmitted wave from the first speed measuring device 20
2 may be received. In such a case, in the first velocity measuring device 201, frequency mixing due to the frequency f _t1 and the frequency f _t2 of the transmission wave from the second velocity measuring device 202 also occurs, and the second velocity measuring device is also generated. in 202, frequency mixing also occurs due to the frequency f _t2 and the frequency f _t1 of the transmitted wave from the first speed measuring device 201, may not be a normal speed measurement, it is called a frequency interference. When the degree of frequency adjustment is large, the mixing detector 8 may not follow up to a high frequency, so there is no particular problem.

[0005]

When a plurality of speed measuring devices are used in close proximity to each other, in addition to the received waves that have been originally subjected to the Doppler effect, the transmitted waves from other speed measuring devices are received. As a result, normal speed measurement may not be possible. In order to prevent such frequency interference, when a plurality of speed measuring devices are installed close to each other, the transmission frequencies are often separated by a certain frequency.
In this case, for example, the set frequency interval Δf is set to Δf = f _t1 −f _t2 (2) as in Expression 2, and Δf is suppressed by the frequency characteristic of the frequency mixing circuit. 2 hours per hour in the 10 GHz band
The Doppler frequency of 00 km / h is about 4 kHz according to the equation (1), the cutoff frequency of the frequency mixing circuit is a low-pass filter of about 4 kHz, and Δf is one digit or more of the cutoff frequency, for example, The above object is achieved by setting the frequency to about 1 MHz. However, if the number of speed measuring devices that are close to each other is increased, there is also a frequency change due to the temperature of the gun oscillator 2, which cannot be solved only by the filter characteristics of the frequency mixing circuit.

The present invention has been made to solve the above-mentioned problems, and a circuit for judging a Doppler signal is added to the receiving circuit of the speed measuring device so as not to be affected by frequency interference. At the same time, it is an object of the present invention to provide a speed measuring device which is not affected by other noises.

[0007]

A speed measuring device according to the present invention is provided with a waveform judging circuit composed of a duty judging circuit and an interval judging circuit so as not to be influenced by frequency interference and to prevent other noise. It was designed so that it would not be affected.

[0008]

According to the present invention, the received Doppler signal is judged by the duty judgment circuit and the interval judgment circuit whether or not it is a normal Doppler signal, and the speed measurement is performed only in the normal condition, and the speed measurement is interrupted in the abnormal condition. Therefore, it is possible to realize a speed measuring device that is not affected by frequency interference and is not affected by other noises.

[0009]

【Example】

Example 1. 1 is a block diagram of a first embodiment of the present invention, in which 41 is a duty judgment circuit, 42 is a duty judgment signal which is the output of the duty judgment circuit 41, 43 is an interval judgment circuit, and 44 is an interval judgment circuit. 43 is the output of the correlation determination signal, 45 is the period determination signal of the interval determination circuit 43, and 46 is the duty determination signal 42, the correlation determination signal 44, and the period determination signal 4.
5 and inputs the AND of the above three types of signals and outputs the waveform judgment signal 47. 48 gates the rectangular wave Doppler signal 12 with the waveform judgment signal 47 and outputs the shaped Doppler signal 49. The output gate circuit 40 is a waveform determination circuit including a duty determination circuit 41, an interval determination circuit 43, an AND circuit 46, and a gate circuit 48. In the figure, reference numerals 1 to 12, 31 to 33 indicate parts equivalent to or corresponding to the same reference numerals in FIG.

Next, the operation of the speed measuring device according to the present invention will be described. In the speed measurement device configured as described above, the transmitted wave 5 that hits the traveling vehicle 1 is reflected and the received wave 6 is received.
Is input to the mixing detector 8 via the path from the antenna 4 to the circulator 3. The mixed detector 8 extracts the Doppler signal 9 which is a mixed detection output by frequency mixing the received wave 6 and the injected wave 7, and extracts the amplified rectangular wave Doppler signal 12. The square wave Doppler signal 12 is
It is supplied to the duty judgment circuit 41 and the interval judgment circuit 43, respectively, and the Doppler waveform is verified. 2A and 2B are diagrams for explaining the operation of the duty determination circuit 41, in which the duty of the rectangular wave Doppler signal 12 is measured and the duty ratio (t / t in FIG. 2A) is measured.
If T) is within a predetermined range (a range of 1/3 to 2/3 in the illustrated example of FIG. 2B), “OK” (meaning Good) is output to the duty determination signal 42. If it deviates from this range, “NG” (meaning “Not good”) is output. That is, if the Doppler signal 9 deviates from a normal sine wave signal, the rectangular wave Doppler signal 12 will be distorted, and the duty ratio will become extremely small or large. The result of whether or not it is a Doppler signal is output to the duty determination signal 42.

3 (a), 3 (b) and 3 (c) are diagrams for explaining the operation of the interval determination circuit 43. As shown in FIG. In the interval determination circuit 43, first, the interval between the waves of the rectangular wave Doppler signal is measured, and the correlation between the periods of the adjacent Doppler waves is tested. Specifically, as shown in FIG. 3B, the correlation between adjacent Doppler waves is obtained by the interval ratio. That is, the interval ratio is within a predetermined range (see FIG.
In the example shown in (b), if the range is 0.7 to 1.5), "OK" (meaning Good) is output to the correlation determination signal 45, and if it is out of this range, "NG" is issued. (N
(meaning ot good) is output. Furthermore, the period for each wave (T1, T2 in the example of FIG. 3A) is measured, and this value is equal to or less than a predetermined value (Ta or less in the example of FIGS. 3C and 3A). For example, "NG" as the cycle determination signal 44
(Means "Not good") is output, and otherwise outputs "OK" (means "Good"). In other words, the cycle determination signal 44 outputs a determination as to whether or not the frequency range is not normally considered in speed measurement. As described above, in the speed measuring device using the radio wave in the 10 GHz band, the Doppler frequency of 200 km / h is approximately 4 kHz according to the equation (1). On the other hand, it is usual that the transmission waves from other speed measuring devices are farther than this, and the above T
When a value of 1/4000 seconds or less is used as a, for example, when the influence of radio waves from another speed measuring device is affected, it can be judged by the cycle judgment signal, and in this case, the speed measurement can be interrupted. .

On the other hand, the AND circuit 46 outputs a waveform determination signal 47 as a logical product of the duty determination signal 42, the correlation determination signal 44 and the period determination signal 45. That is, the waveform determination signal 47 is set to "OK" only when the duty determination signal 42, the correlation determination signal 44, and the cycle determination signal 45 are all in the "OK" state. The gate circuit 48 gates the rectangular wave Doppler signal 12 by the waveform judgment signal 47, supplies the rectangular wave Doppler signal 12 to the counting circuit 11 only when the waveform judgment signal 47 is in the “OK” state, and executes the speed calculation. When the waveform determination signal 47 is in the "NG" state, the rectangular wave Doppler signal 12 is not supplied to the counting circuit 11, so that the speed calculation is not executed.

Example 2. FIG. 4 is a configuration diagram of another embodiment of the present invention. In the figure, 50 is a timer circuit and 51 is a cycle determination holding signal which is an output of the timer circuit 50. In the figure, 1-12, 31-33, 40-49 show the same or equivalent parts as the same reference numerals in FIG. In the figure, the duty judgment circuit 41, the AND circuit 46, and the gate circuit 48 perform the same operations as in the embodiment of FIG. The cycle determination signal 44 output by the interval determination circuit 43 is the "OK" signal output by the timer circuit 50 when the cycle of the Doppler wave is larger than a predetermined value as in the embodiment of FIG. The cycle determination hold signal 51 is set to “O
It outputs a "K" signal. On the other hand, when the period of the Doppler wave is smaller than a predetermined value, the period determination signal 44 has “N
The "G" signal is output. The timer circuit 50 receives the “NG” signal from the cycle determination signal 44 and immediately sets the cycle determination holding signal 51 to the “NG” state. Furthermore, the timer circuit 50 outputs the “NG” state once, and then the period determination holding signal 5 is output for a predetermined time, for example, about 30 minutes.
The “NG” state is continuously output to 1.

Generally, a gun oscillator or the like is used as a microwave source in the velocity measuring device, but the oscillation frequency has a temperature characteristic, and the frequency changes as the temperature changes. Therefore, even if the transmission frequencies are separated from each other by a certain amount in advance between the plurality of speed measuring devices, the frequencies may become close to each other due to the difference in the individual temperature characteristics of the radio wave oscillation sources. FIG. 5 shows FIG.
2 shows a typical example of the oscillation frequency, that is, the transmission frequency from the two speed measuring devices found in the above configuration. FIG. 5 shows that the frequencies gradually approach each other as the temperature changes. By default, as shown is away from the frequency f _t2 and the frequency f _t1 of the first speed measuring device a second speed measuring device, if for frequency interference in the frequency characteristic of the mixing detectors even if It is in the area where no Doppler signal is output.
When a change as shown in FIG. 5 appears as the temperature rises, a Doppler signal is output. Initially, the frequency f _t1 of the first speed measuring device combined with the detection output by both also there are you are away and the frequency f _t2 of the second speed measuring device, a frequency component is high. The mixed detection output by both gradually shifts to a low frequency component as the temperature changes.

[0015] In the embodiment of FIG. 4, detected at the stage where the frequency f _t2 apart between the frequency f _t1 of the first speed measuring device a second speed measuring device interrupts the constant time period measured. Since the temperature change changes with time, the measurement detection can be interrupted even if the mixed detection output shifts to a low frequency component by continuing the “NG” state for a certain time from the cycle determination holding signal 51.

The AND circuit 46 has a duty judgment signal 4
The waveform determination signal 47 is output as the logical product of the value 2, the correlation determination signal 44, and the cycle determination holding signal 51. That is, the waveform determination signal 47 is set to “OK” only when the duty determination signal 42, the correlation determination signal 44, and the cycle determination holding signal 51 are in the “OK” state. The gate circuit 48 gates the rectangular wave Doppler signal 12 by the waveform judgment signal 47, supplies the rectangular wave Doppler signal 12 to the counting circuit 11 only when the waveform judgment signal 47 is in the “OK” state, and executes the speed calculation.
When the waveform determination signal 47 is in the "NG" state, the rectangular wave Doppler signal 12 is not supplied to the counting circuit 11, so that the speed calculation is not executed.

Embodiment 3. FIG. 6 is a block diagram of another embodiment of the present invention, in which 21 is a pulse generator and 2 is a pulse generator.
2 is a modulated pulse 2 based on the output from the pulse generator 21.
It is a frequency divider circuit that outputs 3. In the figure, 1-12, 31-
Reference numerals 33, 40 to 49 denote the same or corresponding portions as the same reference numerals in FIG. In FIG. 6, a velocity measuring device using a so-called pulse modulation method is used, and in this case, the transmission wave does not have the single frequency shown in FIG. 1 but sideband waves due to pulse modulation. In this case, the interference between the sidebands also becomes a problem, and the effect of the waveform determination circuit 40 can be expected as compared with the case of the continuous wave in FIG. As shown in FIG. 1, the operation of the embodiment shown in FIG.
4 and the waveform determination signal 47 are "OK" only when the period determination signal 45 is in the "OK" state. The gate circuit 48 gates the rectangular wave Doppler signal 12 by the waveform judgment signal 47, supplies the rectangular wave Doppler signal 12 to the counting circuit 11 only when the waveform judgment signal 47 is in the “OK” state, and executes the speed calculation. When the waveform determination signal 47 is “NG”,
Since the rectangular wave Doppler signal 12 is not supplied to the counting circuit 11, the speed calculation is not executed.

Example 4. FIG. 7 is a block diagram of another embodiment of the present invention. In the figure, 1 to 12, 31 to 33,
Reference numerals 40 to 49 are the same reference numerals in FIG. 4, 21 to 23 are the same reference numerals in FIG. 6, and 50 and 51 are the same or equivalent portions as the same reference numerals in FIG. FIG. 7 also shows a velocity measuring device using a pulse modulation method. In this case, the transmission wave does not have the single frequency shown in FIG. 4 but sideband waves due to pulse modulation. In this case, the interference between the sidebands also becomes a problem, and the effect of the waveform determination circuit 40 can be expected compared with the case of the continuous wave in FIG. Operation of the embodiment of Figure 7, detected by step away and the frequency f _t2 of the frequency f _t1 and the second speed measuring device of the first speed measuring device as shown in FIG. 4, a predetermined time period Stop the measurement. Since the temperature change changes with time, the measurement detection can be interrupted even if the mixed detection output shifts to a low frequency component by continuing the “NG” state for a certain time from the cycle determination holding signal 51.

The Doppler signal thus received is verified by the duty of the Doppler wave, the correlation of the pulse intervals and the pulse intervals, and the speed is measured only in the normal state, which is effective for the close installation of the speed measuring device. Give means.

[0020]

As described above, the present invention measures the speed only when the Doppler signal is normal, and is extremely effective for close installation of the speed measuring device and erroneous measurement.

[Brief description of drawings]

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

FIG. 2 is a diagram showing the operation of Embodiment 1, Embodiment 2, Embodiment 3 and Embodiment 4 of the present invention.

FIG. 3 is a diagram showing the operation of Embodiment 1, Embodiment 2, Embodiment 3 and Embodiment 4 of the present invention.

FIG. 4 is a configuration diagram of a speed measuring device according to a second embodiment of the present invention.

FIG. 5 is a diagram showing the operation of Embodiments 2 and 4 of the present invention.

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

FIG. 7 is a configuration diagram of a speed measuring device according to a fourth embodiment of the present invention.

FIG. 8 is a block diagram of a conventional speed measuring device.

FIG. 9 is a diagram showing an operation of a conventional speed measuring device.

[Explanation of symbols]

 1 traveling vehicle 2 gun oscillator 3 circulator 4 antenna 5 transmitted wave 6 received wave 7 injection wave 8 mixing detector 9 Doppler signal 10 amplifier 11 counting circuit 12 rectangular wave Doppler signal 20 speed measuring device 21 pulse generator 22 frequency dividing circuit 23 modulation Pulse 23 Modulator 31 First terminal 32 Second terminal 33 Third terminal 40 Waveform determination circuit 41 Duty determination circuit 42 Duty determination signal 43 Interval determination circuit 44 Correlation determination signal 45 Period determination signal 46 AND circuit 47 Waveform determination signal 48 Gate Circuit 49 Shaped Doppler Signal 50 Timer Circuit 51 Period Judgment Hold Signal 201 First Speed Measuring Device 202 Second Speed Measuring Device

Claims (3)

[Claims] 1. The speed of the traveling vehicle is provided with an antenna that emits a radio wave from a radio wave source as a continuous wave toward a traveling vehicle on a road and receives a reflected wave from the traveling vehicle by utilizing the Doppler effect of the radio wave. In a speed measuring device that is configured to measure, a mixing detector that extracts the Doppler by performing frequency mixing of the transmitted wave and the reflected wave, a duty determination circuit that verifies the duty ratio of the Doppler signal, and the Doppler signal. In the above-mentioned duty judgment circuit and interval judgment circuit, which is provided with an interval judgment circuit that measures the cycle of adjacent waveforms and measures the size of the cycle,
The speed is measured only when the duty ratio is within a predetermined range, the change in the period between adjacent waveforms of the Doppler signal is within a predetermined range, and the period of the Doppler signal is equal to or greater than a predetermined value. A speed measuring device characterized in that 2. The speed of the traveling vehicle utilizing an Doppler effect of the radio wave, which is provided with an antenna for radiating a radio wave from a radio source as an intermittent wave toward a traveling vehicle on a road and receiving a reflected wave from the traveling vehicle. In the speed measuring device to measure, a mixing detector for extracting the Doppler by frequency mixing the transmitted wave and the reflected wave, a duty determination circuit for performing a duty ratio test of the Doppler signal, and the Doppler signal It is provided with an interval determination circuit that measures the period of adjacent waveforms and measures the size of the period. In the duty determination circuit and the interval determination circuit, the duty ratio is within a predetermined range, and the Doppler signals are adjacent to each other. Only when the change in the waveform period is within a predetermined range and the Doppler signal period is equal to or greater than a predetermined value A speed measuring device characterized in that the speed is measured. 3. A timer circuit provided between the interval determination circuit and the AND circuit, for interrupting the speed measurement for a predetermined time when the period of the Doppler signal is equal to or less than a predetermined value. The speed measuring device according to claim 1 or 2, further comprising: