JP2501546B2 - Reference time signal generator - Google Patents

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a technique for generating synchronized time signals at a plurality of distant points in order to identify the occurrence location of a phenomenon from the propagation speed of light, electromagnetic waves and the like.

[0002]

2. Description of the Related Art For example, when locating a broken portion of a power transmission line, surge detection means for detecting a surge voltage generated by a lightning strike is connected to the power transmission line at a fixed distance L.
The surge voltage due to a lightning strike or the like is detected by each surge detecting means, the times T ₁ and T ₂ at which the surge voltage arrives are obtained from the time reference signal generator, and the surge voltage arrival time difference ΔT = T ₁ −T is obtained based on these times. _{The method} of calculating ₂ and obtaining the position from each surge detection means is widely used.

By the way, the propagation speed of the surge voltage propagates at an extremely high speed with a delay time determined by the characteristic impedance of the power transmission line. Therefore, in order to obtain a sufficiently high orientation accuracy for practical use, the arrival times of the surge voltages should be several times. It is necessary to measure in about 10 nanoseconds. Although it is relatively easy to measure the time itself with an accuracy of about several tens of nanoseconds, it is extremely difficult to synchronize the time measuring devices at a plurality of points with an accuracy of about several tens of nanoseconds. In other words, when the time standard is terrestrial broadcast wave, not only is the area where the radio waves of the same broadcasting station can be received relatively small, but it is also affected by instability factors such as ghosts due to topography. It becomes extremely difficult to synchronize the time with an accuracy of 10 nanoseconds. For this reason, direct waves from navigation satellites are received and their system time signals are used to generate time data synchronized between a plurality of points. Systems using such navigation satellites can obtain highly accurate and synchronized time signals, but the structure of the electronic devices that make up the system is complicated and expensive, so many systems such as lightning observation systems are used. If it is necessary to install it at the observatory, there is a problem that enormous cost will be required to construct the system.

The present invention has been made in view of the above circumstances, and an object of the present invention is to provide a navigation satellite by a broadcast wave from a broadcasting satellite by using a circuit element commercially available at low cost as a consumer device. It is an object of the present invention to provide a novel reference time synchronization device that can obtain positioning accuracy with an accuracy equal to or higher than the above.

[0005]

In order to solve such a problem, in the present invention, a parent clock signal formed by extracting a vertical synchronization signal from a satellite broadcast wave and the parent clock signal.
Clock to generate a child clock signal synchronized with the clock signal.
Clock generation means and a parent clock for counting the parent clock signal.
Clock counter and a child clock for counting the child clock signal.
Clock counter and the parent clock when requested from the outside
Outputs the count contents of the counter and child clock counter
A counter value acquisition means and a correction means for correcting the arrival time difference of the satellite broadcast waves are provided.

[0006]

[Operation] Since the vertical synchronization signals forming the satellite broadcast wave reach multiple points at the same time regardless of the length of the ground distance in the millisecond order, this is used as the parent clock signal.
Count and make sure that the count values are the same on the equipment at each point.
In other words, the parent clock signal between multiple devices should be synchronized.
It will be Matako clock signal, for each device
It can be independently synchronized to the parent clock signal. Shi
Therefore, the parent clock signal and the child clock signal
Multiple devices that are separated by distance by outputting count values
It is possible to obtain time data with no time error between them.

[0007]

DESCRIPTION OF THE PREFERRED EMBODIMENTS The details of the present invention will be described below with reference to the illustrated embodiments. FIG. 2 shows an embodiment of a transmission line fault point locating device using the reference time signal generator of the present invention. In the figure, reference numerals 1 and 2 are surge detectors, respectively, and a fixed distance L. , Is connected to the power transmission line 3 via the filters 4 and 5 after a distance of 200 meters, for example.
Reference numerals 6 and 7 denote time signal generators, which receive television broadcast radio waves from the broadcast satellite 8 to synchronize time data such as clocks with each other. The time points T ₁ and T ₂ at which the detection signal is output are output to the fault point locating device 9. Reference numerals 10 and 11 in the figure denote parabolic antennas for receiving broadcast radio waves.

FIG. 1 shows an embodiment of a reference time signal generator according to the present invention. Reference numeral 12 in the drawing is a satellite broadcast receiver, which is specified from satellite broadcast waves received by a parabolic antenna 10. The channel selection unit 13 selects the channel of the above and converts the signal into an intermediate frequency that is relatively easy to handle, the intermediate frequency amplification unit 14 that amplifies the signal from this channel, and the video signal processing unit 15 that extracts the video signal. . Reference numeral 20 in the figure denotes a vertical synchronization signal separation unit, which is the video signal processing unit 1.
5, a sync separation circuit 21 for receiving the video signal output from
And a field separation circuit 22, and is configured to selectively output a vertical synchronization signal. Reference numeral 23 is a basic clock generation circuit, which is composed of an oscillation circuit 26 including a crystal oscillator 25 whose temperature is strictly controlled by a constant temperature bath 24. 27 is a reference clock generation circuit,
The alternating signal synchronized with the vertical synchronizing signal is pulse-shaped to form a parent clock signal, and the alternating signal from the basic clock generation circuit 23 is formed to generate a child clock signal, which are output to the circuit in the subsequent stage. Has been done.

A parent clock counter 29 counts the parent clock signal from the reference clock generation circuit 27, and a clock counter 30 counts the child clock signal from the reference clock generation circuit 27. Reference numeral 31 denotes a count value fetch circuit, which is configured to output the count value of each of the counters 29 and 30 as a time signal when receiving an external signal from a device that requests time data. 32
Is a correction circuit configured to store the time difference of arrival of broadcast satellite waves caused by the difference in latitude and longitude of the point where the device is installed, and correct the time difference due to the distance between the installation locations in the area. .

When the device is activated in this embodiment,
The satellite broadcast receiving device 12 receives the direct wave of the broadcast wave emitted from the broadcast satellite. As a result, a signal that is not affected by a ghost or the like can be obtained although a certain time difference occurs depending on the distance connecting the broadcasting satellite and the ground. The reference clock generation circuit 27 is a basic clock generation circuit that synchronously divides the period of the vertical synchronization signal (FIG. 3 (I)) extracted from the satellite broadcast wave by the vertical synchronization signal separation unit 20 and the vertical synchronization signal with extremely high accuracy. And a signal from FIG. 23 ((II) in the figure) are output as a parent clock signal and a child clock signal, respectively. The parent clock counter 29 receives the parent clock signal from the reference clock generation circuit 27 and the child clock counter 30 receives the reference clock generation circuit 27.
Count each child clock signal from.

In this state, when an output request of the clock signal is input from the external device to the count value fetch circuit 31, the count value fetch circuit 31 outputs the count values of the parent clock counter 29 and the child clock counter 30. Correction circuit 3
2, the correction and outputs between difference time rather based on the difference between the distance connecting the broadcasting satellite and terrestrial. The parent clock signal is vertical
From the original signal, and the child clock signal is the parent clock
It is generated based on the signal, so it is placed at each point.
The counter contents of the counters 29 and 30 of the
It means that there is no time data.

According to this embodiment, since the vertical synchronizing signal which is not affected by the program switching is used,
Not only can it provide continuity over a long period of time and a stable signal can be obtained, but it can also be directly applied to other broadcasting systems such as high-definition broadcasting. Further, since the basic clock signal generation circuit 23 is built in, the count value of the child clock counter 30 is used for the time data, so that the synchronization of the satellite broadcast wave can be performed for a relatively long time regardless of the stoppage of the satellite broadcast wave due to food or the like. It is possible to obtain the obtained time signal.

FIG. 4 shows another embodiment of the present invention, in which reference numeral 40 is a basic clock signal generating circuit, which comprises a first PLL circuit 41, a second PLL circuit 40, and a switching circuit 43. ing. The first PLL circuit 41 receives an input of the color subcarrier output from the video signal processing unit 15 and outputs a desired multiplied wave, for example, a triple multiplied wave, which is synchronized with the input, and detects a phase change of the color subcarrier. And outputs a phase change detection signal. 2nd PL
The L circuit 42 receives the input of the color subcarrier and outputs a signal having the same frequency as that of the first PLL circuit 41.
It has a lock function for holding the previous phase by inputting the phase change detection signal from the PLL circuit 41. The switching circuit 43 receives the vertical synchronization signal, the signals from the first PLL circuit 41, and the second PLL circuit 42, and normally receives the first P signal.
The output frequency of the LL circuit 41 is selected, and the output frequency of the second PLL circuit 42 is selected when the vertical synchronizing signal is output.

In operation of the device in this embodiment,
When the color subcarrier of the video signal from the satellite broadcast receiver 12 is input, the first PLL circuit 41 forming the basic clock signal generation circuit 40 instantly synchronizes with the color subcarrier, and is an integral multiple of the color subcarrier, for example, Outputs an alternating signal of 3 times. On the other hand, the second PLL circuit 42 is connected to the first PLL circuit 41.
When a certain period of time has passed from the point of synchronizing with the color subcarrier, an alternating signal of 3 times synchronized with the color subcarrier is output.

In this way, since the phase of the color subcarrier does not change while the same program is being broadcast, the first PLL
The circuit 41 and the second PLL circuit 42 both output an alternating signal synchronized with the color subcarrier, that is, a child clock signal. The reference clock generation circuit 27 is a parent clock signal synchronized with the vertical synchronization signal extracted by the vertical synchronization signal separation unit 20 from the satellite broadcast wave received by the satellite broadcast reception device 11, and a child clock signal synchronized with the color subcarrier. Is output. The parent clock counter 29 counts the parent clock signal from the reference clock generation circuit 27, and the child clock counter 30 counts the child clock signal.
In this state, when an external signal requesting the output of the time signal is input to the count value fetch circuit 31, the count value fetch circuit 31 outputs the count values of the parent clock counter 29 and the child clock counter 30. These values are used as time data by correcting the direct wave arrival time difference caused by the ground distance by the correction circuit 32.

On the other hand, when a phase change occurs in the color subcarrier as in the case where the program is changed, the first PLL circuit 41 instantly synchronizes with the color carrier whose phase has changed, and at the same time, the phase change occurs in the color subcarrier. It outputs a phase change detection signal to notify that. On the other hand, since the response speed of the second PLL circuit 42 is set to be small, the phase change detection signal from the first PLL circuit 41 is transmitted before the second PLL circuit 42 can keep up with the phase delay of the color subcarrier accompanying the change of the program. Will receive. As a result, the second PLL circuit 42 is locked in a state of being synchronized with the color subcarrier before the phase change, and outputs the alternating signal having the same phase as the color subcarrier before the program change. Since the program is changed in accordance with the vertical synchronizing signal, the switching circuit 43 operates at the same time as the phase change and outputs the signal of the second PLL circuit 42 to the reference clock generating circuit 27.

As a result, the switching circuit 43 outputs an alternating signal that is an integral multiple of the color subcarriers that keeps the same phase as much as possible, regardless of the change in the phase of the color subcarriers due to the change of the program. The child clock signal whose phase continuity is maintained is supplied to the child clock counter 30.

(Experimental example) 200 in the direction connecting the terrestrial broadcasting stations.
When terrestrial television broadcasting was received at a distance of meters, the time when the same signal was received was measured, the arrival time difference was calculated from these times, and the distance between the receiving points was calculated.
The distance between the receiving points could be obtained with an error of a few meters. From this, it has been found that it is possible to synchronize a plurality of time signals with extremely high accuracy regardless of the circuit configuration of a consumer product level.

In the above embodiment, two P
Although the child clock signal is generated by using the LL circuit, it is clear that the same operation can be achieved even if the signal synchronized with the color subcarrier is generated by using one PLL circuit. . Further, in the above-mentioned embodiment, the case of applying to the location of the break point of the transmission line and the location of the lightning strike point has been described, but it is required to synchronize a plurality of timing devices arranged at a high distance with high accuracy. Obviously, it can be applied to various other systems described.

[0020]

As described above, in the present invention ,
A master clock constructed by extracting the vertical synchronization signal from satellite broadcast waves.
Child clock signal synchronized with lock signal and parent clock signal
Clock generating means for generating a signal and a parent clock signal
And a parent clock counter that counts
A child clock counter to count and a parent according to an external request
The count contents of the clock counter and child clock counter
Since a counter value fetching means for outputting and a correcting means for correcting the arrival time difference of satellite broadcast waves are provided, a simple circuit structure is provided.
Configuration of the parent clock and child clock signals between multiple devices.
Time that can be synchronized and has no time error between multiple devices
A device that outputs data can be realized.

[Brief description of drawings]

FIG. 1 is a block diagram of an apparatus showing an embodiment of the present invention.

FIG. 2 is a configuration diagram showing a transmission line accident locating system in which the time synchronization device of the present invention is used.

FIG. 3 is a waveform chart showing the operation of the above apparatus.

FIG. 4 is a block diagram showing another embodiment of the present invention.

[Explanation of symbols]

 12 satellite broadcasting receiver 20 vertical sync signal separation unit 23 basic clock generation circuit

 ─────────────────────────────────────────────────── ─── Continuation of the front page (56) Reference JP-A 61-191985 (JP, A) JP-A 60-160777 (JP, A) JP-A 2-226092 (JP, A) JP-A 62- 105077 (JP, A) JP 58-60884 (JP, A) JP 2-20912 (JP, A)

Claims (1)

(57) [Claims] From 1. A satellite broadcast wave to extract the vertical synchronizing signal
The configured parent clock signal and the same as the parent clock signal.
Reference clock generating means for generating a desired child clock signal
And a parent clock counter for counting the parent clock signal
And a child clock counter for counting the child clock signal
And the parent clock counter and
Counter value acquisition that outputs the count contents of the child clock counter
A reference time signal generation device comprising an input unit and a correction unit for correcting the arrival time difference of the satellite broadcast waves.