JPH11234255A - Clock reproducing system, transmission station and reception station to be used for the same - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a clock reproducing system, a transmission station and a reception station therefor with which the generation of a time lag in clock reproducing processings required from the reception of a carrier wave transmitted from each transmission station, for example, to a demodulating processing is eliminated. SOLUTION: A reception station 30 previously transmits to a transmission station 20 a clock signal to be used for extracting effective data from a carrier wave sent from a transmission station 20 after modulating it to a carrier wave using a frequency for clock transmission independent of the effective data through narrow band digital transmission equipment 33. The transmission station 20 receives the carrier wave, reproduces the clock signal by extracting and demodulating the signal of a frequency component for clock transmission through narrow band digital reception equipment 22 and sends the effectctive data while modulating them to the carrier wave synchronized with the clock signal through main digital transmission equipment 23.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a transmitting station which transmits valid data as a carrier, a receiving station receives the carrier, and reproduces a clock signal synchronized with the carrier. The present invention relates to a clock recovery system that demodulates a carrier wave to extract valid data based on a signal and a transmitting station and a receiving station used in the system, and in particular, to shorten the time from the reception of the carrier wave by the receiving station to the demodulation process. It is something devised.

[0002]

2. Description of the Related Art Generally, in a transmission system, for example, a carrier transmitted by a transmitting station is received by an antenna device at a receiving station, and a clock signal synchronized with the carrier is reproduced. , A received signal obtained by the antenna device is demodulated to extract valid data.

By the way, in a normal transmission system, a clock signal is reproduced by using a received signal obtained by the antenna device. However, after the reception is started by the antenna device, the clock signal is reproduced and demodulated. By the time, a certain time lag occurs. In particular, a transmission method (TD) in which signals from a plurality of transmitting stations are temporally multiplexed.
In Time Division Multiple Access (MA), this time lag occurs each time the transmitting station changes, which causes a problem in system operation.

[0004]

As described above, in the conventional transmission system, the receiving station receives the carrier transmitted from the transmitting station, reproduces the clock signal from the received signal, and then reproduces the clock signal. Since the received signal is demodulated based on the signal, there is an inconvenience that a certain time lag occurs between the time of receiving the carrier and the time of demodulation.

SUMMARY OF THE INVENTION An object of the present invention is to provide a clock recovery system which can eliminate the occurrence of a time lag due to a clock recovery process required from the reception of a carrier to the demodulation process for a carrier transmitted from each transmitting station. The purpose of the present invention is to provide a transmitting station and a receiving station which are used for the above.

[0006]

According to the present invention, in order to achieve the above object, one receiving station transmits a clock signal used for extracting valid data from a carrier wave transmitted from the other transmitting station. The data is modulated into a carrier using a clock transmission frequency independent of the effective data and is transmitted in advance, and the other transmitting station receives the carrier and extracts a clock transmission frequency component signal. The clock signal is reproduced by demodulation, and the effective data is modulated into a carrier wave synchronized with the clock signal and transmitted.

More specifically, a receiving station receives a carrier transmitted from a transmitting station, and transmits a carrier modulated with a clock signal to the transmitting station. Clock signal generating means for generating a clock signal for extracting effective data from the carrier wave, and modulating the clock signal generated from the clock signal generating means to a clock transmission frequency, and transmitting the carrier signal to the receiving station antenna apparatus as a carrier wave. A transmitting station side antenna device for receiving a carrier wave transmitted from the receiving station and transmitting a carrier wave obtained by modulating effective data, and a transmitting station. By extracting the signal of the clock transmission frequency component from the carrier received by the side antenna device and demodulating it, the clock signal And the clock signal reproducing means for reproducing,
Based on the clock signal reproduced by the clock signal regenerating means, there is provided a valid data modulation transmitting means for modulating valid data into a carrier wave and outputting it to the transmitting station side antenna device.

According to this configuration, the receiving station modulates the clock signal for extracting the effective data from the carrier transmitted from the transmitting station into a carrier using the clock transmission frequency, and transmits the modulated signal to the transmitting station in advance. The transmitting station receives the carrier transmitted from the receiving station, extracts the clock transmission frequency component signal, demodulates the signal, reproduces the clock signal, and modulates the effective data into a carrier based on the clock signal. By transmitting the data, the receiving station receives the carrier wave, so that the effective data can be demodulated and extracted using the clock signal of the own station.

As a result, since the receiving station can demodulate the carrier transmitted from the transmitting station using the clock signal of the own station, it is not necessary to regenerate a new clock signal every time a new carrier is received. In addition, it is possible to eliminate a time lag that occurs from the reception of the carrier wave to the demodulation processing.

When the receiving station receives a carrier wave transmitted from a plurality of transmitting stations by switching the transmitting station for each transmitting station, the receiving station notifies the transmitting station of its own clock signal in advance to each transmitting station. If a carrier modulated based on the signal is transmitted, the receiving station does not regenerate a new clock signal during the carrier receiving process, so that even if the transmitting station is switched, the receiving station can receive the signal. Signals are not interrupted, and carrier waves can be continuously received from each transmitting station.

In the above configuration, even if the receiving station has no means for transmitting the clock signal to the transmitting station, the carrier wave and the transmission signal transmitted from the receiving station having the means for transmitting the clock signal can be obtained. A receiving station-side antenna device for receiving a carrier wave transmitted from a station; and a receiving station-side clock for reproducing a clock signal by extracting a signal of a clock transmission frequency component from the carrier wave received by the receiving station-side antenna device. Reproducing means, and valid data extracting means for demodulating a carrier wave from the transmitting station received by the receiving station antenna device and extracting valid data based on the clock signal reproduced by the receiving station clock reproducing means. I am preparing for it.

According to this configuration, the carrier transmitted from the receiving station having the means for transmitting the clock signal is received, and the signal of the frequency component for clock transmission is extracted and demodulated, so that the signal transmitted from the transmitting station is transmitted. Separately from the carrier receiving process, a clock signal for extracting valid data from the carrier from the transmitting station can be reproduced, and the clock signal is used to extract valid data from the carrier transmitted from the transmitting station. This eliminates the need to perform clock recovery from the carrier wave on which the effective data is modulated, and eliminates the time lag that occurs between the time of receiving the carrier wave and the process of demodulation.

[0013]

Embodiments of the present invention will be described below in detail with reference to the drawings. FIG. 1 shows an embodiment of a clock recovery system according to the present invention, and FIG. 2 shows frequency characteristics applied to the embodiment.

The clock recovery system in FIG. 1 is applied to a satellite transmission system such as SNG (Satellite News Gathering), and modulates a main digital signal as effective data including at least video data and the like to a transmission frequency, and then modulates the carrier signal. (Shown by a solid line in FIG. 1) to the transmitting station 20 for transmission to the satellite 10 and a carrier transmitted from the transmitting station 20 for transmission from the satellite 10 to reproduce a clock signal synchronized with the carrier. Receiving stations 30 and 40 for demodulating a received signal based on the clock signal and extracting a main digital signal.

Here, the relationship between the transmitting station 20 and the receiving station 30 will be described. The receiving station 30 includes a reference clock generator 32 that generates a clock signal for demodulating a main digital signal from a received signal obtained from an antenna device 31 that has received a carrier wave. The clock signal generated from the reference clock generator 32 is a carrier using the narrow band clock transmission frequency shown in FIG. 2 in the narrow band digital transmitter 33 (indicated by a dotted line in FIG. 1).
And transmitted to the space by the antenna device 31.

The transmitting station 20 receives the carrier transmitted from the receiving station 30 via the satellite 10 with the antenna device 21. Then, the antenna device 21 receiving this carrier wave
Is output to the narrowband digital receiver 22. The narrow-band digital receiver 22 reproduces a clock signal by extracting a signal of a clock transmission frequency component that is a narrow band from the input received signal and demodulates the signal, and outputs the clock signal to the main digital transmitter 23. The main digital transmission device 23 modulates a main digital signal including video data into a carrier wave synchronized with a clock signal provided by the narrowband digital reception device 22 and transmits the modulated carrier to the satellite 10 via the antenna device 21.

The carrier wave (shown by a solid line in FIG. 1) transmitted from the transmitting station 20 is received by the antenna device 31 of the receiving station 30. Then, a received signal obtained by the antenna device 31 that has received the carrier is output to the main digital receiving device 34. The main digital receiving device 34 extracts a main digital signal by demodulating a received signal provided from the antenna device 31 based on a clock signal generated from the reference clock generating device 32.

Next, the relationship between the receiving station 30 and the receiving station 40 will be described. That is, the receiving station 40
, Received by the antenna device 41,
The obtained reception signal is output to the narrowband digital receiver 42. The narrow-band digital receiving device 42 reproduces a clock signal by extracting and demodulating a signal of a clock transmission frequency component from the input received signal, and outputs the clock signal to the main digital receiving device 43. Thereafter, the receiving station 40 receives the carrier wave transmitted from the transmitting station 20 by the antenna device 41, and outputs the obtained received signal to the main digital receiving device 4
Supply 3 The main digital receiving device 43 extracts a main digital signal including video data and the like by demodulating a received signal obtained by the antenna device 41 that has received the carrier wave based on a clock signal provided from the narrowband digital receiving device 42. I do.

In the above embodiment, the transmitting station 20
Can be similarly implemented when there are a plurality of. Therefore, according to the above embodiment, the receiving station 30 is connected to the transmitting station 2
The clock signal for extracting the main digital signal from the carrier wave transmitted from 0 is transmitted to the narrow band digital transmission device 33.
Is modulated into a carrier using a clock transmission frequency and transmitted to the transmitting station 20 side in advance. The transmitting station 20 receives the carrier transmitted from the receiving station 30 by the antenna device 21, At 22, a clock signal is reproduced by extracting and demodulating a signal of a clock transmission frequency component from the received signal, and a main digital signal is modulated into a carrier by a main digital transmission device 23 based on the clock signal. And send it out. The receiving station 30 receives the carrier wave from the transmitting station 20 so that the main digital signal can be demodulated and extracted using the clock signal of the own station.

For this reason, since the receiving station 30 can demodulate the carrier transmitted from the transmitting station 20 using the clock signal of the own station, it is necessary to regenerate a new clock signal every time a new carrier is received. This eliminates the time lag that occurs from the reception of the carrier wave to the demodulation processing.

This is effective in the case of a TDMA system in which a plurality of transmitting stations exist, such as a multiple relay in an SNG system, and transmission signals of each transmitting station are multiplexed in time and transmitted. In the case of this TDMA system, as in the past,
If the receiving station has a clock regeneration function, a routine to regenerate the clock occurs every time the transmitting station changes,
During that time, reception is interrupted. In contrast, using the method of the above embodiment, the carrier transmitted from each transmitting station is:
Since the clock signal is synchronized with the clock signal transmitted from the receiving station, it is not necessary to regenerate a new clock signal for each transmitting station. Therefore, even if the transmitting station changes, the receiving signal is cut off at the receiving station side. This makes it possible to continuously receive carrier waves from each transmitting station.

In the receiving station 40, the receiving station 30
Receiving the carrier wave transmitted from the transmitting station, and extracting and demodulating the signal of the clock transmission frequency component, the transmitting station 2
A clock signal can be regenerated separately from the receiving process of the carrier transmitted from 0, and the clock signal can be used to extract the main digital signal from the carrier transmitted from the transmitting station 20. It is not necessary to perform clock recovery from the carrier wave itself in which the digital signal has been modulated, and it is possible to eliminate the time lag that occurs between the time when the carrier wave is received and the time when the demodulation process is performed.

Further, in a general satellite transmission system, a communication line such as an OW (Order Wire) is often provided. Therefore, the clock signal is modulated from the receiving station 30 to the transmitting station 20 using this communication line. By transmitting a carrier wave, it is not necessary to newly provide a line or a transmission / reception facility, and it is possible to suppress an increase in facilities and costs.

It should be noted that the present invention is not necessarily limited to the scope of the above-described embodiment, and it is needless to say that various modifications can be made without departing from the spirit of the present invention.

[0025]

As described in detail above, according to the present invention,
For example, for a carrier transmitted from each transmitting station, a clock recovery system that can eliminate the occurrence of a time lag due to clock recovery processing required from the time of receiving the carrier to the time of demodulation, and a transmitting station and a receiving station used in this system Can be provided.

[Brief description of the drawings]

FIG. 1 is a block diagram showing an embodiment of a clock recovery system according to the present invention.

FIG. 2 is a diagram showing frequency characteristics applied to the embodiment.

[Explanation of symbols]

 DESCRIPTION OF SYMBOLS 10 ... Satellite, 20 ... Transmitting station, 21, 31, 41 ... Antenna device, 22, 42 ... Narrow band digital receiving device, 23 ... Main digital transmitting device, 30, 40 ... Receiving station, 32 ... Reference clock generating device, 33 ... narrow band digital transmitter, 34, 43 ... main digital receiver.

Claims (11)

[Claims] 1. After modulating valid data to a transmission frequency,
A transmitting station transmitting as a carrier, receiving a carrier transmitted from the transmitting station, regenerating a clock signal synchronized with the carrier, demodulating the carrier based on the clock signal, and demodulating the effective data. A receiving station that extracts the valid signal from the carrier transmitted from the transmitting station, and outputs a clock signal that is independent of the transmission frequency. Modulated to a carrier using a transmission frequency and pre-transmitted to the transmitting station, wherein the transmitting station receives the carrier transmitted from the receiving station and generates a signal of the clock transmission frequency component. The clock signal is reproduced by extracting and demodulating it, and the valid data is modulated and transmitted to a carrier wave synchronized with the clock signal. Clock recovery system characterized in that it was. 2. The receiving station side antenna device, wherein the receiving station receives the carrier transmitted from the transmitting station, and sends a carrier modulated with the clock signal to the transmitting station;
Clock signal generating means for generating the clock signal for extracting the valid data from the carrier wave received by the receiving station side antenna device; and a clock signal generated by the clock signal generating means for converting the clock signal to the clock transmission frequency. And a clock modulation transmitting unit that outputs the carrier as the carrier to the receiving station side antenna device, wherein the transmitting station receives the carrier transmitted from the receiving station and modulates the effective data. And a clock signal reproducing means for reproducing the clock signal by extracting and demodulating a signal of the clock transmission frequency component from a carrier received by the transmitting station antenna device for transmitting the clock signal. Based on the clock signal reproduced by the clock signal reproducing means,
2. The clock recovery system according to claim 1, further comprising effective data modulation transmission means for modulating the effective data into a carrier wave and outputting the modulated data to the transmitting station side antenna device. 3. After modulating valid data to a transmission frequency,
A transmitting station transmitting as a carrier, receiving a carrier transmitted from the transmitting station, regenerating a clock signal synchronized with the carrier, demodulating the carrier based on the clock signal, and demodulating the effective data. The first to extract
A clock recovery system including a second receiving station, wherein the first receiving station outputs the clock signal for extracting the valid data from the carrier transmitted from the transmitting station, The transmission station and the second station modulate the carrier wave using an independent clock transmission frequency.
By transmitting to the receiving station in advance, the transmitting station receives the carrier wave transmitted from the first receiving station, extracts the signal of the clock transmission frequency component and demodulates by extracting Regenerate a clock signal, modulate the valid data into a carrier wave synchronized with the clock signal, and transmit the carrier signal. The second receiving station receives the carrier wave transmitted from the first receiving station and transmits the clock signal. The clock signal is reproduced by extracting and demodulating a signal of a frequency component for use, and the effective data is extracted by demodulating a carrier transmitted from the transmitting station based on the clock signal. Clock recovery system. 4. The first receiving station side antenna device that receives the carrier wave transmitted from the transmitting station, and sends out a carrier wave obtained by modulating the clock signal to the transmitting station, Clock signal generating means for generating the clock signal for extracting the valid data from the carrier received by the first receiving station side antenna device;
Clock modulation transmitting means for modulating a clock signal generated from the clock signal generating means to the clock transmission frequency and outputting the modulated signal as the carrier to the first receiving station side antenna device; A transmitting station-side antenna device for receiving the carrier wave transmitted from the first receiving station and transmitting a carrier wave obtained by modulating the valid data; and a clock transmission frequency component from the carrier wave received by the transmitting station-side antenna device. A transmitting station side clock signal reproducing means for reproducing the clock signal by extracting and demodulating the signal of
Based on the clock signal reproduced by the transmitting-station-side clock signal reproducing means, modulating the valid data into a carrier wave and outputting the modulated data to the transmitting-station-side antenna device; A receiving station configured to receive a carrier wave transmitted from the first receiving station and a carrier wave transmitted from the transmitting station; and a carrier wave received by the second receiving station side antenna apparatus. By extracting and demodulating the signal of the clock transmission frequency component from
Receiving station side clock recovery means for recovering the clock signal, and based on the clock signal recovered by the reception station side clock recovery means, demodulates the carrier received by the second receiving station side antenna device, 4. The clock recovery system according to claim 3, further comprising valid data extracting means for extracting valid data. 5. After modulating valid data to a transmission frequency,
Applied to a satellite transmission system including a plurality of transmitting stations transmitting to a satellite as a carrier, and a receiving station receiving a carrier transmitted from the plurality of transmitting stations and relaying the satellite,
A clock recovery system for recovering a clock signal synchronized with a carrier received by the receiving station, and then demodulating the carrier based on the clock signal to extract the valid data, wherein the receiving station comprises: The clock signal for extracting the effective data from the carrier transmitted from a station, the clock signal is modulated to a frequency for clock transmission independent of the transmission frequency, and transmitted to the plurality of transmitting stations in advance as a carrier. The plurality of transmitting stations receive the carrier transmitted from the receiving station and relayed the satellite, and regenerate the clock signal by extracting and demodulating a signal of the clock transmission frequency component, A clock recovery system wherein valid data is modulated and transmitted to a carrier wave synchronized with the clock signal. 6. The receiving station side antenna device, wherein the receiving station receives the carrier transmitted from the plurality of transmitting stations and relays the satellite, and transmits a carrier modulated with the clock signal to the transmitting station; Clock signal generating means for generating the clock signal for extracting the valid data from the carrier wave received by the receiving station side antenna device; and a clock signal generated by the clock signal generating means for converting the clock signal to the clock transmission frequency. And a clock modulation transmitting unit that modulates a frequency in a band to a frequency determined in advance for each transmitting station and outputs the carrier wave to the receiving station side antenna device, wherein the transmitting station transmits the satellite transmitted from the receiving station. A transmitting-station-side antenna device for receiving the carrier wave relayed by the transmitting station and transmitting a carrier wave obtained by modulating the effective data; A clock signal reproducing unit that reproduces the clock signal by extracting and demodulating the signal of the clock transmission frequency component corresponding to the own station from the carrier received by the device, and a clock signal reproducing unit that reproduces the clock signal. 6. The clock recovery system according to claim 5, further comprising: effective data modulation transmitting means for modulating the effective data into a carrier wave based on a clock signal and outputting the modulated data to the transmitting station antenna apparatus. 7. After modulating valid data to a transmission frequency,
The present invention is applied to a satellite transmission system including a plurality of transmitting stations transmitting to a satellite as a carrier, and first and second receiving stations receiving a carrier transmitted from the plurality of transmitting stations and relaying the satellite. 1. A clock recovery system for recovering a clock signal synchronized with a carrier received by a second receiving station, and then demodulating the carrier based on the clock signal to extract the valid data. The receiving station modulates the clock signal for extracting the valid data from the carrier transmitted from the transmitting station and relaying the satellite, to a carrier using a clock transmission frequency independent of the transmission frequency. Before transmitting to the transmitting station and the second receiving station, and the plurality of transmitting stations are transmitted from the first receiving station before relaying the satellite. The clock signal is reproduced by receiving a carrier wave, extracting a signal of the clock transmission frequency component and demodulating the signal, modulating the valid data to a carrier wave synchronized with the clock signal, and transmitting the valid data. The receiving station receives the carrier transmitted from the first receiving station and relayed the satellite, extracts the signal of the clock transmission frequency component, and demodulates the signal by reproducing the clock signal. A clock recovery system, wherein a carrier wave transmitted from the transmitting station is demodulated based on the data to extract the valid data. 8. The first receiving station receives the carrier transmitted from the transmitting station and relaying the satellite, and transmits the carrier modulated with the clock signal to the transmitting station and the second carrier.
A first receiving station-side antenna device for transmitting to the receiving station, and a clock signal generating means for generating the clock signal for extracting the valid data from the carrier wave received by the first receiving station-side antenna device; Clock modulation transmitting means for modulating a clock signal generated from the clock signal generating means to the clock transmission frequency and outputting the modulated carrier signal to the first receiving station side antenna apparatus as the carrier wave; A transmitting station-side antenna device that receives the carrier transmitted from the first receiving station and relays the satellite, and sends out a carrier modulated with the valid data;
A transmitting-station-side clock signal reproducing unit that reproduces the clock signal by extracting and demodulating the signal of the clock transmission frequency component from the carrier wave received by the transmitting-station-side antenna device; Effective data modulation transmitting means for modulating the valid data into a carrier wave based on the clock signal reproduced by the reproducing means and outputting the modulated data to the transmitting station side antenna device, wherein the second receiving station comprises: A second receiving station that receives a carrier transmitted from the receiving station and the transmitting station and relaying the satellite.
A receiving-station-side antenna device and a receiving-station-side clock recovery device that recovers the clock signal by extracting and demodulating a signal of the clock transmission frequency component from the carrier wave received by the second receiving station-side antenna device. Means,
Valid data extracting means for demodulating the carrier wave received by the second receiving station antenna apparatus and extracting the valid data based on the clock signal reproduced by the receiving station clock reproducing means. The clock recovery system according to claim 7, wherein 9. When a transmitting station modulates valid data into a transmission frequency and transmits the data as a carrier, the carrier receives the carrier, reproduces a clock signal synchronized with the carrier, and then reproduces the clock. A receiving station that demodulates the carrier based on a signal to extract the valid data; a receiving station-side antenna device that receives the carrier transmitted from the transmitting station; and Clock signal generating means for generating the clock signal for extracting the valid data from a carrier wave; and modulating the clock signal generated from the clock signal generating means to the clock transmission frequency independent of the transmission frequency. Clock modulation transmitting means for transmitting the carrier as the carrier to the transmitting station via the receiving station side antenna device. The receiving station, wherein the transmitting station modulates the valid data into a carrier wave synchronized with the clock signal and transmits the modulated carrier signal. 10. A transmitting station that modulates effective data to a transmission frequency and then sends out the carrier as a carrier to a receiving station, wherein a clock signal used to demodulate the carrier from the receiving station to the effective data is the transmission frequency and When a modulated signal arrives at a carrier using an independent clock transmission frequency, a transmitting station-side antenna device that receives the carrier transmitted from the receiving station and sends out a carrier modulated with the effective data, A transmitting-station-side clock signal reproducing unit that reproduces the clock signal by extracting and demodulating the signal of the clock transmission frequency component from the carrier received by the transmitting-station-side antenna device; Means for modulating the effective data into a carrier wave based on the clock signal recovered by the means, Transmitting station, characterized by comprising comprises an effective data modulation transmitting means for outputting the location. 11. When a transmitting station modulates valid data into a transmission frequency and transmits the modulated data as a carrier, the carrier receives the carrier, reproduces a clock signal synchronized with the carrier, and then reproduces the clock. In a receiving station that demodulates the carrier based on a signal to extract the valid data, a clock signal used to demodulate the carrier into the valid data from another receiving station is transmitted by a clock independent of the transmission frequency. When the signal arrives after being modulated into a carrier wave using the receiving frequency, a receiving station-side antenna device that receives a carrier wave transmitted from the other receiving station and a carrier wave transmitted from the transmitting station, Reception of reproducing the clock signal by extracting and demodulating a signal of the clock transmission frequency component from the received carrier wave Office clock recovery means; and valid data for extracting the valid data by demodulating the carrier wave received by the second reception station antenna device based on the clock signal recovered by the reception station clock recovery means. A receiving station comprising extraction means.