JP4363715B2 - Performance station apparatus and satellite digital broadcasting apparatus equipped with performance station apparatus - Google Patents

Description

[0001]
BACKGROUND OF THE INVENTION
The present invention relates to a performance place apparatus that broadcasts digital television signals via a satellite and a satellite digital broadcast apparatus that includes the performance place apparatus .
[0002]
[Prior art]
In a satellite digital broadcasting device, video, audio, and data signals are multiplexed at a performance place located on the ground, and a TS signal having a predetermined frame configuration is generated. The TS signal generated at the performance room is transmitted to the uplink station through a network line or the like. The uplink station combines TS signals sent from a plurality of performance centers by time division multiplexing to generate a combined TS signal. The synthesized TS signal is then subjected to transmission path coding and phase modulation, and transmitted to the satellite as a broadcast wave. The satellite amplifies the broadcast wave transmitted from the uplink station and retransmits it toward the ground.
[0003]
In the satellite digital broadcasting apparatus described above, in the uplink station, TS signals transmitted from a plurality of performance stations are synthesized by time division multiplexing to generate a synthesized TS signal. In this case, it is necessary that the clock for generating the TS signal at each performance place and the reference clock for generating the composite TS signal at the uplink station are synchronized. For this reason, the clock of each performance place and the reference clock of the uplink station are configured to be synchronized.
[0004]
As a method of synchronizing the clock of each performing place with the reference clock of the uplink station, a method of sending a reference clock for synchronization from the uplink station to each performing place using a network or the like, or for synchronization There is a method of sending a signal that can reproduce the reference clock. In these methods, a TS signal is transmitted from the performance station to the uplink station, while a reference clock for synchronization is transmitted from the uplink station to the performance station. In this case, the network is used bidirectionally, and the network usage fee is expensive.
[0005]
In order to solve such a problem, there are an asynchronous method and a pseudo-synchronous method in which the network is used only in one direction.
[0006]
The asynchronous system is a method in which an uplink station is provided with a frequency shift absorbing buffer that absorbs a frequency shift between a performance room clock and an uplink station reference clock, for example. In such a configuration, the frequency shift absorption buffer is reset periodically using a time when there is little influence on broadcasting, or immediately before a frequency shift that cannot be absorbed by the frequency shift absorption buffer occurs, for a certain period of time. This is a method of absorbing the frequency shift generated in the above.
[0007]
The pseudo-synchronization method monitors the frequency shift between the performance clock and the uplink reference clock in the uplink station, and adds a null TS signal or deletes the null TS signal. Thus, it is a method of absorbing the frequency shift between them.
[0008]
Since the asynchronous method and the pseudo-synchronous method use the network only in one direction, the network usage fee is reduced. However, in the case of the asynchronous system due to the frequency shift between the clock of each performance place and the reference clock of the uplink station, there is a problem that the reset interval of the frequency shift absorbing buffer is shortened and the reset is frequently performed. In the case of the pseudo-synchronization method, an expensive pseudo-synchronization device is required, and the processing of the null TS signal at the time of hierarchical switching becomes complicated.
[0009]
Therefore, in order to solve the above problems, there is a method for receiving broadcast waves transmitted from satellites at each performance place, demodulating the received broadcast waves, and extracting a synthesized TS signal or a TS signal of the own station. is there. In this method, a clock synchronized with the extracted synthesized TS signal or the TS signal of the local station is generated, and a TS signal is generated using this clock.
[0010]
Here, a conventional satellite digital broadcasting apparatus will be described with reference to FIG. 4 by taking as an example a method of extracting a synthesized TS signal and generating a clock for TS signal generation. Reference numerals 40A and 40B denote performance stations that generate TS signals. Reference numeral 50 denotes an uplink station that synthesizes a plurality of TS signals transmitted from the performance stations 40A and 40B. Reference numeral 60 denotes a satellite that relays a broadcast wave transmitted from the uplink station 50 and retransmits it toward the ground. Each performance place 40A, 40B has the same configuration. Here, the configuration and operation of the performance place 40A will be described, and the description of the configuration and operation of the performance place 40B will be omitted.
[0011]
The performance place 40A includes a clock reproduction device 41, a multiplexing device 42, and the like. The clock recovery device 41 includes a receiving unit 41a that receives a broadcast wave transmitted from the satellite 60, and a playback unit 41b that demodulates the broadcast wave to extract a synthesized TS signal and generates a clock synchronized with the synthesized TS signal. Has been. The reproduction clock generated by the reproduction unit 41 b is sent to the multiplexing device 42. Multiplexer 42 multiplexes video signals, audio signals, and data based on the recovered clock to generate a TS signal for the local station. The generated TS signal is sent to the uplink station 50 through the network line N, for example. A similar TS signal is also sent to the uplink station 50 from the other performance room 40B.
[0012]
Uplink station 50 synthesizes TS signals sent from a plurality of performance centers 40A and 40B by time division multiplexing based on clock C generated by clock generator 54 in synthesizer 51. Next, the synthesized TS signal is subjected to transmission path coding and phase modulation in the uplink 52 and transmitted to the satellite 60 as a broadcast wave. The satellite 60 relays the broadcast wave transmitted from the uplink station 50 and transmits it to the ground.
[0013]
According to the above-described configuration, when the performance stations 40A and 40B generate their own TS signals, the performance stations 40A and 40B demodulate the synthesized TS signal from the broadcast wave and synchronize with the clock for synthesizing the TS signal in the uplink station or this clock. A clock having a frequency assigned to each performance place is extracted and a reproduction clock synchronized with these clocks is used. Therefore, the reproduction clock for generating the TS signal of each performance place 40A, 40B and the clock of the uplink station 50 are kept synchronized.
[0014]
In addition, when combining a plurality of TS signals in the synthesizer 51, the uplink station 50 includes a TS clock generation clock at each of the performance stations 40 </ b> A and 40 </ b> B and a clock of the uplink station 50. In order to be able to cope with the case where there is a frequency shift, a frequency shift absorbing buffer (not shown) is provided for each of the performance stations 40A and 40B.
[0015]
[Problems to be solved by the invention]
A conventional satellite digital broadcasting apparatus demodulates a synthesized TS signal or the like from a broadcast wave at a performance station, and uses a clock for synthesizing the TS signal of an uplink station or a clock of a frequency assigned to each performance station synchronized with this clock. A TS signal is generated using a recovered clock that is extracted and synchronized with these clocks. In this case, the network is used only in one direction for transmitting the TS signal. However, there may be times when broadcast waves cannot be received during operation, such as when the weather conditions deteriorate, or when switching from the active device to the standby device due to maintenance or failure of the equipment constituting the uplink station. . In such a case, the TS signal cannot be demodulated and extracted from the received broadcast wave, and the reproduction clock for generating the TS signal and the reference clock of the uplink station cannot be synchronized. Further, if the delay time fluctuates due to Doppler shift accompanying the movement of the satellite, the phase of the recovered clock for TS signal generation and the reference clock of the uplink station may be greatly shifted due to the influence.
[0016]
The present invention solves the above-mentioned drawbacks, and synchronizes the clock for TS signal generation with the clock of the uplink station in a performance place against the influence of deterioration of weather conditions, interruption of broadcast waves, influence of Doppler shift of broadcast waves, etc. It is an object of the present invention to provide a performance device and a satellite digital broadcasting device including the performance device with suppressed deviation.
[0017]
[Means for Solving the Problems]
The present invention combines a performance device that generates TS signals for digital broadcasting, and a plurality of TS signals respectively transmitted from a plurality of performance devices based on a reference clock generated by a clock generator. And an uplink station apparatus that transmits the synthesized TS signal as a broadcast wave to the ground via a satellite. The performance apparatus demodulates the synthesized TS signal from the broadcast wave transmitted from the satellite, and the uplink A satellite that extracts a clock for synthesizing a TS signal of a station apparatus or a clock having a frequency assigned to each performance station apparatus synchronized with the clock, and generates a TS signal using the first clock synchronized with the extracted clock in digital broadcasting system, the performance office device, in advance, a clock for generating a second clock based on the oscillation signal that is in accordance with the frequency of the reference clock When a normal TS signal cannot be detected from the broadcast wave transmitted from the satellite, the second clock is selected instead of the first clock, and the TS signal is converted using the second clock. It is characterized by generating.
[0018]
DETAILED DESCRIPTION OF THE INVENTION
An embodiment of the present invention will be described with reference to FIG.
[0019]
Reference numerals 10A and 10B are performance stations that generate TS signals, reference numeral 20 is an uplink station that synthesizes a plurality of TS signals sent from the performance stations 10A and 10B, and reference numeral 30 is sent from the uplink station 20. It is a satellite that relays incoming broadcast waves and retransmits them to the ground. In addition, each performance place 10A, 10B has the same structure. Therefore, here, the configuration and operation of the performance place 10A will be described, and the description of the configuration and operation of the performance place 10B will be omitted.
[0020]
The performance place 10A includes a clock reproduction device 11, a multiplexing device 12, and the like. The clock recovery device 11 receives a broadcast wave transmitted from the satellite 30 and extracts a synthesized TS signal of an uplink station, and a reproducing unit that generates a recovered clock synchronized with the extracted synthesized TS signal. 11b and the like. The reproduction clock generated by the reproduction unit 11 b is sent to the multiplexing device 12. The multiplexer 12 multiplexes the video signal, audio signal, and data based on the reproduction clock to generate the TS signal of its own station. The generated TS signal is sent to the uplink station 20 through the network line N, for example. At this time, a similar TS signal is also sent to the uplink station 20 from the other performance room 10B.
[0021]
In the uplink station 20, TS signals sent from the plurality of performance stations 10A and 10B are respectively added to the frequency shift absorbing buffers 21a and 21b, the reproduction clocks of the performance stations 10A and 10B, and the reference of the uplink station 20 A frequency shift from the clock is absorbed. Thereafter, the TS signal sent from each of the performance stations 10A and 10B is synthesized by time division multiplexing based on the clock C generated by the clock generator 25 and added to the synthesizer 22. Next, the synthesized TS signal is subjected to transmission path coding, phase modulation, and the like on the uplink 23 and transmitted to the satellite 30 as a broadcast wave. The satellite 30 amplifies the broadcast wave sent from the uplink station 20 and retransmits it toward the ground.
[0022]
According to the configuration described above, the TS signals are generated in the performance stations 10A and 10B with the reproduction clock synchronized with the synthesized TS signal in the uplink station 20. Therefore, the reproduction clock for generating the TS signal of each performance place 10A, 10B and the reference clock C of the uplink station 20 are kept synchronized.
[0023]
Here, one example of the frequency / phase shift absorption buffers 21a and 21b will be described with reference to FIG. The frequency / phase shift absorption buffers 21a and 21b are constituted by, for example, a FIFO or the like, and are constituted by an input terminal IN for inputting a signal, a memory 31, an output terminal OUT, and the like. Then, a signal input from the input terminal IN is stored in the memory 31 under the control of the write signal C1. Further, it is read from the memory 31 under the control of the read signal C2.
[0024]
According to this configuration, the frequency of the output signal read from the memory 31 is determined by the read signal C2. Therefore, if the timing of reading from the memory 31 is adjusted by the read signal C2 in consideration of the frequency shift and the phase shift due to the Doppler shift or the like, the frequency / phase shift is absorbed until the buffer fails.
[0025]
Next, the configuration of the clock reproduction device 11 in the performance room 10A will be described with reference to FIG. In FIG. 3, parts corresponding to those in FIG.
[0026]
In the receiving section 11a of the performance place 10A, the received broadcast wave is demodulated by the demodulator 13, and for example, a synthesized TS signal is taken out. The extracted synthesized TS signal is sent to the TS signal detector 14 and the clock regenerator 15 of the regenerating unit 11b. The TS signal detector 14 detects whether the demodulated TS signal is normal or abnormal. The clock regenerator 15 extracts a clock for synthesizing the TS signal of the uplink station or a clock having a frequency assigned to each performance place synchronized with this clock, and a regenerated clock synchronized with the extracted clock. Is generated. The recovered clock is then applied as a reference synchronization signal to the phase locked loop 16 through the terminal A of the switch circuit SW. An oscillation signal from the voltage controlled oscillator 17 is also added to the phase locked loop 16. The phase locked loop 16 controls the frequency of the oscillation signal of the voltage controlled oscillator 17 so as to synchronize with the frequency of the reproduction clock supplied as the reference synchronization signal. In this case, the recovered clock is synchronized with the frequency of the synthesized TS signal of the uplink station. Therefore, the frequency of the oscillation signal of the voltage controlled oscillator 17 is synchronized with the frequency of the TS signal synthesis clock of the uplink station. The oscillation signal of the voltage controlled oscillator 17 is sent to the multiplexer 12 (FIG. 1) and used as a clock signal for generating a TS signal.
[0027]
With the configuration described above, the clock for TS signal generation in each of the performance stations 10A and 10B and the clock of the uplink station 20 are kept synchronized.
[0028]
By the way, in the receiving unit 11a having the above-described configuration, when the weather condition deteriorates and the reception intensity of the broadcast wave becomes weak, or when the broadcast wave is interrupted, a normal TS signal cannot be detected from the broadcast wave. At this time, the TS signal generation clock of each performance place and the uplink station clock cannot be synchronized. In such a case, the TS signal detector 14 detects an abnormality of the TS signal, and the switch circuit SW is switched to the terminal B side.
[0029]
On the terminal B side, a high-precision oscillator 18 that generates an oscillation signal of a predetermined frequency and a clock generator 19 that generates a clock for generating a TS signal from the oscillation signal of the high-precision oscillator 18 are connected. As the high-precision oscillator 18, a high-precision oscillator based on rubidium or cesium excitation is used, and is adjusted in advance to the frequency of the reference oscillator clock of the uplink station 20. When the switch circuit SW is switched to the terminal B side, the clock generated by the clock generator 19 is added to the phase locked loop 16 as a reference synchronization signal. At this time, the frequency of the oscillation signal of the voltage controlled oscillator 17 is synchronized with the frequency of the clock of the clock generator 19. Since the oscillation signal of the high-accuracy oscillator 18 is matched to the frequency of the clock of the uplink station 20, even if the clock is switched, the synchronization shift is suppressed as described later.
[0030]
When the clock of the clock generator 19 is used, the frequency shift is small, but if this state continues, the phase shift becomes large, causing the equipment of the uplink station 20 to malfunction. However, such a phase shift can be easily absorbed by the frequency shift absorbing buffers 21a and 21b of the uplink station 20, and a malfunction of a device in the uplink station 20 can be prevented.
[0031]
A phase locked loop 16 is also provided. Therefore, when the clock applied as the reference synchronization signal to the phase locked loop 16 is switched to the clock generated by the clock generator 19, even if there is a frequency shift between the clocks, the voltage controlled oscillator is operated by the operation of the phase locked loop 16. The oscillation signal changes gradually. For this reason, the TS generator is not shocked by clock switching.
[0032]
In the above-described embodiment, the composite TS signal is extracted from the received broadcast wave and the TS signal generation clock is generated from the extracted composite TS signal in the performance place. In this case, the TS signal of the own station can be further extracted from the synthesized TS signal, and the TS signal generation clock can be generated from the TS signal of the own station. According to the configuration described above, frequency deviation can be suppressed to the accuracy of the high-precision oscillator even during a period in which the broadcast wave cannot be normally received. Further, even when a phase shift occurs due to the Doppler shift of the satellite when demodulating the TS signal from the broadcast wave, such a phase shift can be easily absorbed by the frequency shift absorption buffer of the uplink station. In this case, the required buffer amount is sufficiently smaller than the buffer amount required in the asynchronous method. If the frequency deviation is large, resetting of the frequency deviation absorption buffer can be used together. In this case, the interval between resets becomes long, and frequent resets are not necessary.
[0033]
In the case of a satellite digital broadcasting device, the period of being asynchronous, that is, the period in which the TS signal cannot be correctly demodulated from the broadcast wave is about several hours per month. In addition, there are not so many periodic inspections and malfunctions of uplink stations. For this reason, the asynchronous period that occurs when switching between the active machine and the spare machine is only momentary due to periodic inspections or breakdowns, and the amount of use of the frequency shift absorption buffer can be kept small. For example, assuming that the lifetime of the satellite is about 10 years or more, resetting can be substantially eliminated by taking a sufficient buffer amount.
[0034]
In addition, when the uplink station has a configuration for absorbing frequency deviation, the buffer for absorbing frequency deviation is usually reset when the power is turned on again during periodic inspection or the like. The periodic inspection of the synthesizer is performed in a period shorter than the lifetime of the satellite. Therefore, if the frequency deviation absorbing buffer is reset during periodic inspection of the synthesizer, it is almost unnecessary to reset the absorbing buffer during operation.
[0035]
【The invention's effect】
According to the present invention, interruption of deterioration and broadcast waves of the weather conditions, with respect to such influence of the Doppler shift of the broadcast waves, suppressed synchronization deviation between the clock and the uplink station clock for TS signal generation in playing stations playing A satellite digital broadcasting apparatus equipped with a station apparatus and a performance station apparatus can be realized.
[Brief description of the drawings]
FIG. 1 is a circuit configuration diagram for explaining an embodiment of the present invention.
FIG. 2 is a circuit configuration diagram for explaining a frequency shift absorbing buffer used in the present invention.
FIG. 3 is a circuit configuration diagram for explaining a clock recovery device used in the present invention;
FIG. 4 is a circuit configuration diagram for explaining a conventional example.
[Explanation of symbols]
10A, 10B ... performance station 20 ... uplink station 30 ... satellite 11 ... clock regenerator 11a ... receiver 11b ... reproducer 12 ... multiplexer 13 ... demodulator 14 ... TS signal detector 15 ... clock regenerator 16 ... phase Synchronous loop 17 ... Voltage controlled oscillator 18 ... High precision oscillator 19 ... Clock generators 21a, 21b ... Frequency / phase shift absorbing buffer 22 ... Synthesizer 23 ... Uplink 31 ... Memory N ... Network circuit SW ... Switch

Claims (7)

A performance device that generates a TS signal for digital broadcasting, and a composite TS signal obtained by combining a plurality of TS signals respectively transmitted from a plurality of performance devices based on a reference clock generated by a clock generator And an uplink station apparatus that transmits to the ground via a satellite as a broadcast wave, and the performance station apparatus demodulates a composite TS signal from the broadcast wave transmitted from the satellite, In a satellite digital broadcasting device that extracts a clock for signal synthesis or a clock having a frequency assigned to each performance device synchronized with the clock, and generates a TS signal using the first clock synchronized with the extracted clock , the playing office device, in advance, set a clock generator for generating a second clock based on the oscillation signal that is in accordance with the frequency of the reference clock When a normal TS signal cannot be detected from the broadcast wave transmitted from the satellite, the second clock is selected instead of the first clock, and the TS signal is generated using the second clock. A featured satellite digital broadcasting device. A performance device that generates a TS signal for digital broadcasting, and a composite TS signal obtained by combining a plurality of TS signals respectively transmitted from a plurality of performance devices based on a reference clock generated by a clock generator And an uplink station apparatus that transmits to the ground via a satellite as a broadcast wave, and the performance station apparatus demodulates a composite TS signal from the broadcast wave transmitted from the satellite, and the TS of the uplink station apparatus In a satellite digital broadcasting device that extracts a clock for signal synthesis or a clock having a frequency assigned to each performance device synchronized with the clock, and generates a TS signal using the first clock synchronized with the extracted clock , the playing office device, in advance, an oscillator for generating an oscillation signal that is in accordance with the frequency of the reference clock, the second clock from said oscillation signal A clock generator to generate, a voltage controlled oscillator having a phase-locked loop, and a reference sync signal to be input to the phase-locked loop when a normal TS signal cannot be detected from a broadcast wave transmitted from the satellite. A satellite digital broadcasting device characterized by comprising a switch for switching from one clock to the second clock and generating a TS signal using an oscillation signal generated by the voltage-controlled oscillator.   The satellite digital broadcasting apparatus according to claim 1 or 2, wherein the performance apparatus is provided with a TS signal detector for detecting whether the TS signal demodulated from the broadcast wave is normal or abnormal.   3. The satellite digital broadcasting apparatus according to claim 2, wherein the oscillator uses rubidium or cesium excitation.   A frequency / phase shift in which the uplink station apparatus absorbs the frequency shift between the TS signal synthesis clock of the uplink station apparatus and the first clock or the second clock of the performance apparatus, or the phase shift caused by the Doppler shift of the satellite. The satellite digital broadcasting apparatus according to claim 1, further comprising an absorption buffer. A performance device that generates a TS signal for digital broadcasting, and a composite TS signal obtained by combining a plurality of TS signals respectively transmitted from a plurality of performance devices based on a reference clock generated by a clock generator And an uplink station apparatus that transmits to the ground via a satellite as a broadcast wave, and the performance station apparatus demodulates a composite TS signal from the broadcast wave transmitted from the satellite, In a satellite digital broadcasting device that extracts a clock for signal synthesis or a clock having a frequency assigned to each performance device synchronized with the clock, and generates a TS signal using the first clock synchronized with the extracted clock , each of the plurality of playing locations apparatus, in advance, an oscillator for generating an oscillation signal that is in accordance with the frequency of the reference clock, either the oscillation signal A clock generator for generating a second clock, a voltage-controlled oscillator having a phase-locked loop, and reference synchronization input to the phase-locked loop when a normal TS signal cannot be detected from a broadcast wave transmitted from the satellite A satellite digital broadcasting apparatus, comprising: a switch for switching a signal from the first clock to the second clock; and generating a TS signal using an oscillation signal generated by the voltage-controlled oscillator. A plurality of performance apparatus that generates TS signals for digital broadcasting and a plurality of TS signals respectively transmitted from the plurality of performance apparatuses are synthesized based on a reference clock generated by a clock generator. A performance station apparatus in a satellite digital broadcasting apparatus including an uplink station apparatus that transmits a composite TS signal as a broadcast wave to the ground via a satellite, and demodulates the composite TS signal from the broadcast wave transmitted from the satellite And a demodulating means that performs a first TS signal synthesizing from the synthesized TS signal demodulated by the demodulating means, or a clock having a frequency assigned to each performance apparatus synchronized with the clock. a clock extracting means for extracting a clock, previously, to generate a second clock based on the oscillation signal that is in accordance with the frequency of the reference clock When the normal TS signal is detected from the clock generation means and the broadcast wave transmitted from the satellite, the first clock is selected, and when the normal TS signal cannot be detected, the second clock is selected. A performance apparatus comprising: clock selecting means for generating a TS signal using the clock selected by the clock selecting means.

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