JPH1127659A - Satellite broadcasting system - Google Patents

Abstract

(57) [Summary] [PROBLEMS] To improve the convenience of a viewer in a broadcast receiving apparatus so that channel switching in a received multiplexed broadcast signal can be performed at high speed with good responsiveness. SOLUTION: When terrestrial broadcasting stations BC1 and BC2 code-division multiplex and broadcast a plurality of channels of broadcasting signals via a geostationary satellite SAT to a broadcasting receiver MS in a service area and broadcast the signals, each of the terrestrial broadcasting stations BC1 and BC2 After matching the spreading code phase between the channels, they are multiplexed and transmitted, or the terrestrial broadcasting stations BC1 and BC2 in the geostationary satellite SAT.
Detecting the spread code phase difference between the channels of the CDM broadcast signal arriving from, and matching the spread code phase between the channels based on the detection result, and then transmitting the signal to the broadcast receiver MS. It is.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a satellite broadcasting system for broadcasting information such as video, audio and data to a specific terrestrial service area using a broadcasting satellite or a communication satellite in a geosynchronous orbit. Code division multiplexing (CD
The present invention relates to a system for multiplex broadcasting a plurality of channels by adopting an M (Code Division Multiplex) method.

[0002]

2. Description of the Related Art In recent years, various communication systems have been developed in accordance with the increase in communication needs and the development of communication technologies. Among them, there is a satellite broadcasting system using a geostationary orbit broadcasting satellite or a communication satellite. An advantage of the satellite broadcasting system is that information broadcasting services can be provided to a wide range of service areas without installing a large-scale infrastructure on the ground.

[0003] Incidentally, a satellite broadcasting system which has been conventionally operated is an analog system, and a plurality of channels are frequency division multiplexed (FDM).
x) Broadcast in a multiplexed manner. But,
This type of system has a low degree of multiplicity of channels per frequency, and cannot cope with a demand for channel expansion accompanying recent multimedia.

Therefore, recently, research and development of digital satellite broadcasting systems have been actively conducted. In this case, as a channel multiplexing method, for example, orthogonal frequency division multiplexing (OFDM) is used.
lex) system and Code Division Mu (CDM)
ltiplex) is being considered.

[0005]

However, there are various problems that must be solved in order to apply these multiplexing systems to a satellite broadcasting system. In particular, the CDM system synchronizes a spread code of a receiving apparatus with a broadcasting signal. It takes a long time, for example, ten and several seconds, to be established. For this reason, in the receiving device, it takes a long time until the channel switching is completed after the channel switching operation is performed, and the viewer has to wait for a long time for each channel switching, and feels discomfort. In some cases,
Some troubles such as failure to obtain important information during the channel switching period occurred, so measures were needed.

The present invention has been made in view of the above circumstances. It is an object of the present invention to provide a broadcast receiving apparatus capable of performing high-speed switching of channels in a received multiplexed broadcast signal with good responsiveness. It is an object of the present invention to provide a satellite broadcasting system that improves the convenience of viewers.

[0007]

In order to achieve the above object, a satellite broadcasting system according to the present invention provides code division by spreading and combining broadcast signals of a plurality of channels with different spread codes for each channel. Multiplexing means for multiplexing, and transmission synchronizing means for setting a phase relationship of spread codes between broadcast signals of respective channels code division multiplexed by the multiplexing means to a predetermined synchronization state. It is something to do.

As a result, according to the present invention, the phase relationship of the spread codes between the channels of the multiplexed broadcast signal is set to a predetermined synchronization state in a terrestrial broadcast station or a geostationary satellite, for example. Therefore, in the broadcast receiving apparatus, if the multiplexed broadcast signal is received and spread code synchronization is established for any of the channel signals, when a switching operation to another channel is performed, Based on the phase relationship between the channels, it is possible to establish spread code synchronization with the switching destination channel signal in a short time.
Therefore, high-speed channel switching with excellent responsiveness can be performed, thereby reducing the irritability of the viewer and reducing the possibility of losing important information during the channel switching period.

Further, the satellite broadcasting system of the present invention detects a phase difference of a spread code between each channel signal of a code division multiplexed broadcast signal at a terrestrial broadcast station or a geostationary satellite, and detects a phase difference between the detected spread codes. Means for notifying the broadcast receiving apparatus of information representing the phase difference, wherein the broadcast receiving apparatus receives the information representing the phase difference, and performs code division received via a geostationary satellite based on the information representing the phase difference. The spread code synchronization for each channel of the multiplexed broadcast signal is established.

According to the present invention, even if the spread code between the channels of the multiplexed broadcast signal is not synchronized, the phase difference of the spread code between the channels is detected, and this phase difference information is received by broadcasting. The device is notified. Therefore, in the broadcast receiving apparatus, if the multiplexed broadcast signal is received and spread code synchronization is established for any of the channel signals, when a switching operation to another channel is performed,
Based on the notified phase difference information, it is possible to establish spread code synchronization with the switching destination channel signal in a short time. Therefore, also in this case, high-speed channel switching with excellent responsiveness can be performed.

Further, according to the satellite broadcasting system of the present invention, when there are a plurality of terrestrial broadcasting stations which transmit a broadcast signal by spreading a spectrum with a different spreading code for each channel, the channel of the broadcast signal transmitted by these terrestrial broadcasting stations The phase difference of the spread code between them is detected by a geostationary satellite, and this phase difference information is reported from the geostationary satellite to each of the terrestrial broadcasting stations as the transmission source. Then, in each terrestrial broadcast station, based on the notified phase difference information, the transmission timing of a broadcast signal to be transmitted by its own device is variably controlled for each channel, and thereby each terrestrial broadcast station transmits The spread code phase difference of the broadcast signal is set to zero on the geostationary satellite.

That is, a feedback control loop of the broadcast signal transmission timing is formed between the geostationary satellite and each terrestrial broadcast station, so that the spread code phase of each broadcast signal transmitted by a plurality of terrestrial broadcast stations is changed on the geostationary satellite. The transmission timing of each terrestrial broadcast station is variably controlled so as to always match.

By doing so, even if there are a plurality of terrestrial broadcast stations, the spread code phases of the broadcast signals transmitted by these terrestrial broadcast stations always coincide on the geostationary satellite. Therefore, a geostationary satellite transmits a broadcast signal received from each terrestrial broadcast station to a broadcast receiver while maintaining the reception timing, so that the broadcast receiver always spreads each broadcast signal transmitted by a plurality of terrestrial broadcast stations with a spread code. It can be received in a synchronized state. For this reason, in the broadcast receiving apparatus, if spread code synchronization is established for any of the broadcast signals arriving from each terrestrial broadcast station, if the switching operation to another channel is performed, the switching is performed in a short time. It becomes possible to establish spread code synchronization with a broadcast signal of another terrestrial broadcast station. Therefore, high-speed channel switching with excellent responsiveness can be performed.

[0014]

BEST MODE FOR CARRYING OUT THE INVENTION

(First Embodiment) FIG. 1 is a schematic configuration diagram showing a first embodiment of a satellite broadcasting system according to the present invention.

This satellite broadcasting system includes a plurality of terrestrial broadcasting stations (VSAT) BC1 and BC2 or feeder link stations, a geostationary satellite SAT, and a satellite tracking control station STCC.

A terrestrial broadcasting station (VSAT) BC1, BC2 or a feeder link station transmits program information created and edited by each broadcasting company to a Ka band (26.5 to 40GH).
z) or the transmission to the geostationary satellite SAT via the Ku band (12.5 to 18 GHz) uplink transmission path.

The geostationary satellite SAT includes, for example, a Ka band or Ku band antenna having a diameter of 2.5 m class,
S band (for example, 2.6 GH) having a diameter of 15 m class
z) antenna. The broadcast signal multiplexed from each of the broadcasting stations (VSAT) BC1 and BC2 or the feeder link station is received and amplified by the Ka or Ku band antenna, and then converted to an S band signal. Then, the converted broadcast signal is transmitted from the S band antenna to the service area via the S band downlink transmission path. The diameter of the antenna for uplink transmission mounted on the geostationary satellite SAT may be smaller than 2.5 m class, and the diameter of the S-band antenna is not limited to 15 m class but may be 8 m class.

The satellite tracking control station STCC monitors and controls the operation state of the geostationary satellite SAT. In the service area, for example, a broadcast receiver (not shown) fixedly installed in an office or a home, or an in-vehicle or portable mobile broadcast receiver MS is provided by the geostationary satellite SAT.
To receive the broadcast signal transmitted to the S-band downlink transmission path. In the S-band downlink transmission path, 64 to 2
A plurality of channels having a transmission rate of 56 Kbps / channel are multiplexed up to 900 channels. When a video signal is transmitted by each channel, MPEG4 (moving picture experts group 4) is used as a video encoding method.

By the way, the terrestrial broadcasting stations BC1 and BC2 of the first embodiment have a function of matching the phases of the spread codes between the respective channels when transmitting a plurality of programs by code division multiplexing. And is configured as follows. FIG. 2 is a circuit block diagram showing the configuration of the transmission unit.

That is, broadcast signals of a plurality of programs (N programs in the figure) edited by a circuit (not shown) are input to the modulators 11 to 1n, respectively. These spread modulators 11-1
n respectively transmit the broadcast signal to a spreading code generator 21.
2n are subjected to spread spectrum modulation using different spreading codes generated from. Broadcast signals that have been spread-spectrum-modulated by the respective spread modulators 11 to 1n are combined by the combiner 31 into 1
After being combined with a system code division multiplex (CDM) broadcast signal, the signal is input to the modulator 32. In the modulator 32, the CDM broadcast signal is further modulated by a digital modulation method such as QPSK or QAM. The modulated CDM broadcast signal is frequency-converted by the transmitter 33 into a Ka or Ku band radio signal, further amplified to a predetermined transmission power level, and transmitted from the antenna 34 to the geostationary satellite. .

The terrestrial broadcasting station MS has a control circuit 40. The control circuit 40 generates a reference phase signal for designating a reference phase of the spread code, and supplies the reference phase signal to each of the spread code generators 21 to 2n. Each of the spreading code generators 21 to 2n starts generating a spreading code in synchronization with the reference phase signal supplied from the control circuit 40.

With such a configuration, the broadcast signals of the respective programs are respectively transmitted to the spread modulators 11 to 1n by the spread codes generated in synchronization with the reference phases from the respective spread code generators 21 to 2n. It is spread modulated.
Therefore, the CDM multiplex broadcast signal output from the synthesizing circuit 31 has the same spread code phase between the respective channels, and the CDM broadcast signal having the same spread code phase is transmitted to the broadcast receiving apparatus via the geostationary satellite SAT. Broadcast to MS.

Accordingly, in the broadcast receiving apparatus MS, for example, when the power is turned on, the above-mentioned C arriving via the geostationary satellite SAT
If the spread code synchronization is established for any one channel of the DM broadcast signal, then the spread code corresponding to all the channels is generated in the same phase, and the switching operation to another channel is performed. If
It is possible to synchronize and receive in a very short time only by switching the spread code without establishing spread code synchronization again for this channel.

(Second Embodiment) In a second embodiment of the present invention, a terrestrial broadcasting station BC1,
The spread code phase difference between the channels of the CDM broadcast signal arriving from the BC2 is detected, and based on the detection result, the spread code phases between the channels are matched, and then the broadcast receiving apparatus MS
It is intended to be transmitted to.

FIG. 3 is a circuit block diagram showing the configuration of the geostationary satellite SAT according to the second embodiment. In the figure, C transmitted from each of the terrestrial broadcasting stations BC1 and BC2
The DM broadcast signal is received by a Ku-band receiving antenna 51 and then input to a receiving circuit 52. Then, after being subjected to low-noise amplification and down-conversion to an intermediate frequency signal, the signal is distributed and input to k correlators 61 to 6k. The number of correlators 61 to 6k is determined by each terrestrial broadcasting station BC.
1 and BC2 are set corresponding to the total number k of channels to be multiplexed. In these correlators 61 to 6k, spectrum despreading of the received intermediate frequency signal is performed using a spreading code preset for each channel. Then, the received signals after despreading are input to spreading modulation circuits 71 to 7k, respectively.

In the correlators 61 to 6k, when the received intermediate frequency signal is despread in spectrum, the received intermediate frequency signal and a spread code (such as a Walsh code or a Gold code prepared separately from the PN code) are used. (The orthogonal code of the control circuit 8).
Input to 0. The control circuit 80 detects the phase difference between the orthogonal code generated by the geostationary satellite SAT and the received orthogonal code based on the correlation values input from the correlators 61 to 6k for each channel. Then, a phase control signal for reducing the detected phase difference to zero is generated for each channel, and these phase control signals are generated by the spread modulation circuits 71 to 7.
k.

The spread modulation circuits 71 to 7k adjust the generation phases of the spread codes based on the phase control signals given from the control circuit 80, respectively. Then, the received signals input from the correlators 61 to 6k are spread with this spread code, and the broadcast signal after the spread processing is input to the synthesizing circuit 53. In the synthesizing circuit 53, each of the spread modulators 7
Each of the broadcast signals output from 1 to 7k is synthesized, and the CDM broadcast signal obtained by the synthesis is converted to a frequency conversion circuit 54.
Is input to

In the frequency conversion circuit 54, the CDM broadcast signal is frequency-converted to an S-band frequency (2.6 GHz) given to its own system, and input to the transmitter 55. The transmitter 55 amplifies the frequency-converted CDM broadcast signal to a predetermined transmission power level, and transmits the CDM broadcast signal from the S-band transmission antenna 56 to the service area.

With such a configuration, the phase difference of the spread code of each channel signal of the CDM broadcast signal transmitted by each of the terrestrial broadcast stations BC1 and BC2 is detected by the geostationary satellite SAT, and the detected phase difference is reduced to zero. After being spread spectrum again by the spreading code phase controlled to
It is transmitted in the S band toward the service area. For this reason, even if the spread code phases between the channels of the CDM broadcast signals arriving from the terrestrial broadcast stations BC1 and BC2 do not match, this phase difference is transmitted after being absorbed by the geostationary satellite SAT and transmitted. Received at the MS.

Therefore, in the broadcast receiving apparatus MS, for example, when the power is turned on, the above-mentioned C arriving via the geostationary satellite SAT
If the spread code synchronization is established for any one channel of the DM broadcast signal, even if a switching operation to another channel is performed thereafter, the spread code synchronization is not established again for this channel, and the spread code synchronization is established. Just by switching the code, it is possible to synchronize and receive in an extremely short time.

(Third Embodiment) In a third embodiment of the present invention, when the terrestrial broadcasting stations BC1 and BC2 generate and transmit a CDM broadcast signal, the phase difference between the spreading codes of the respective channels is detected. The phase difference information is multiplexed with the CDM broadcast signal and transmitted. Then, when the broadcast receiving apparatus MS selectively receives each channel of the CDM broadcast signal arriving via the geostationary satellite SAT, the chip phase of the spreading code is determined based on the phase difference information received together with the CDM broadcast signal. Initially, the broadcast code of each channel is selectively spectrum-despread and reproduced by this spreading code.

FIG. 4 is a circuit block diagram showing the configuration of the transmitting sections of the terrestrial broadcasting stations BC1 and BC2 according to this embodiment. 2, the same parts as those in FIG. 2 are denoted by the same reference numerals, and detailed description is omitted.

The spread codes generated by the spread code generators 21 to 2n are input to the phase difference information transmitting circuit 41. The phase difference information transmitting circuit 41 detects the phase difference of each of the spread codes with respect to the reference phase, and information representing these phase differences is encoded and primary-modulated, and then input to the spread modulator 43. The spread modulator 43 spreads the spectrum of the phase difference information input from the phase difference information transmission circuit 41 using the spread code generated from the spread code generator 42 and inputs the spread spectrum information to the synthesis circuit 35. The combining circuit 35 combines the spread modulation signal of each channel broadcast signal output from the spread modulators 11 to 1n with the spread modulation signal of the phase difference information output from the spread modulator 42, and transmits the combined signal. It is provided to the modulator 32.

On the other hand, the broadcast receiving apparatus MS is configured as follows. FIG. 5 is a circuit block diagram showing the configuration.
That is, the CDM broadcast signal arriving from the geostationary satellite SAT is received by the S-band receiving antenna 91, is input to the receiving circuit 92, is subjected to low-noise amplification, and is frequency-converted into an intermediate frequency signal. The received intermediate frequency signal is distributed and input to the first and second correlators 93 and 94.

The first correlator 93 despreads the received intermediate frequency signal with a spread code corresponding to the reception channel specified by the control circuit 90, and detects the despread channel signal with a detector. (DET) 95. The designation of the reception channel is performed by the user operating the remote control operation unit 97. In the detector 95, the channel signal is detected by, for example, a detection method corresponding to the QPSK method, and the received broadcast signal obtained by the detection is input to the audio / video separation circuit 101.

The audio / video separation circuit section 101 separates the reproduced reception signal into audio data, video data, and additional data including text data, and inputs the separated received audio data to the audio decoder 102. The received video signal is input to the video decoder 104, and the additional data is input to the additional data decoder 103. The audio decoder 102 decodes the received audio data to reproduce an audio signal, and outputs the audio signal from the speaker 105. Further, the video decoder 104 decodes the received video data according to, for example, the MPEG4 system, and causes the decoded video signal to be displayed on a display 106 composed of a liquid crystal display.
Further, the additional data decoder 103 decodes the additional data composed of text data and the like, and causes the display 106 to display the decoded data together with the video signal.

On the other hand, in the second correlator 94, the received intermediate frequency signal output from the receiving circuit 92 is spectrum despread by a spreading code prepared in advance for transmitting phase difference information. Then, the phase difference information signal obtained by the despreading is detected and decoded by the detector 96 and then input to the control circuit 90.

The control circuit 90 designates a spreading code corresponding to the designated channel to the first correlator 93 every time a channel switching operation is performed by the operation section 97, and based on the phase difference information. Specify the phase of the set spreading code. Therefore, in the first correlator 93, a spread code corresponding to the reception channel specified by the control circuit 90 is generated from the specified chip phase, and the received intermediate frequency signal is despread by the spread code. You.

In such a system, the terrestrial broadcasting stations BC1 and BC2 multiplex the CDM broadcast signal and information representing the spread code phase difference of each channel with the CDM broadcast signal and transmit the multiplexed information. On the other hand, in the broadcast receiving apparatus MS, the phase difference information is separated and extracted from the CDM broadcast signal, the chip phase of the spread code is initialized based on the phase difference information, and the broadcast code of a desired channel is set by the spread code. Is spectrally despread and reproduced.

Therefore, when the terrestrial broadcasting stations BC1 and BC2 transmit the broadcast signal of each channel by spreading the spectrum using a spreading code, even if the spread signal is spread without synchronizing the spread code between the channels, the broadcast receiving apparatus MS
In addition to the above-mentioned CDM broadcast signal, terrestrial broadcast stations BC1, B
The chip phase of the spread code is initialized based on the phase difference information sent from C2, and the spread code causes the CDM broadcast signal to be spectrum despread. Therefore, compared with the case where synchronization is established by searching for a spreading code for each channel, spreading code synchronization with respect to each channel can be established in a short time, whereby channel switching can be performed with good responsiveness. Can be done to speed.

(Fourth Embodiment) In a fourth embodiment of the present invention, when the terrestrial broadcasting stations BC1 and BC2 generate and transmit a CDM broadcasting signal, the phase difference of the spreading code of each channel is detected. The phase difference information is multiplexed with the CDM broadcast signal and transmitted. Then, in the geostationary satellite SAT, the phase difference information is separated and extracted, and each channel signal of the CDM broadcast signal is spectrum-spread again by a spreading code whose phase is set based on the phase difference information and transmitted to the service area. It was done.

FIG. 6 shows a geostationary satellite S according to this embodiment.
FIG. 2 is a circuit block diagram illustrating a configuration of an AT. 3, the same parts as those in FIG. 3 are denoted by the same reference numerals, and detailed description is omitted.

The geostationary satellite SAT is provided with a correlator 57 for separating and extracting phase difference information, in addition to correlator groups 61 to 6k for despreading the spectrum of the CDM broadcast signal for each channel. is there. The correlator 57 despreads the received intermediate frequency signal output from the receiving circuit 52 with a predetermined spreading code for transmitting phase difference information, thereby separating and extracting the phase difference information.

The control circuit 81 generates a phase control signal for designating the chip phase of the spreading code of each channel based on the phase difference information separated and extracted by the correlator 57, and converts these phase control signals. Each spread modulation circuit 71-7
Give to k.

Each of the spread modulation circuits 71 to 7k initializes a chip phase of a spread code in accordance with the phase control signal, and converts each channel signal once subjected to spectrum despreading by the correlators 61 to 6k to the initial phase. The spectrum is spread again using the set spreading code. Each spread modulator 7
Each of the channel signals re-spread by 1 to 7k is combined by the combining circuit 53 to become a CDM broadcast signal. Then, the frequency is converted to an S-band frequency by a frequency conversion circuit 54, further amplified to a predetermined transmission power level by a transmitter 55, and transmitted from an S-band transmission antenna 56 to a terrestrial service area.

With such a configuration, the terrestrial broadcasting station B
Even if C1 and BC2 multiplex and transmit the broadcast signals of the respective channels without spread code synchronization between the channels, the CDM broadcast signals transmitted from the terrestrial broadcast stations BC1 and BC2 will not In the SAT, the spectrum is spread again based on the phase difference information transmitted by the terrestrial broadcasting stations BC1 and BC2 at the same time, and is transmitted to a terrestrial service area.

Therefore, the broadcast receiving apparatus MS receives the CDM broadcast signal synchronized with the spread code between the channels. Therefore, in the broadcast receiving apparatus MS, the CD
As long as the spread code synchronization for any one channel of the M broadcast signal is established, it is possible to separate and reproduce the broadcast signal of the desired channel simply by switching the spread code, without renewing the spread code synchronization for the other channels. it can. Therefore, channel switching can be performed at high speed with good responsiveness. Further, in this embodiment, since it is not necessary to provide each broadcast receiving apparatus MS with a circuit for initially setting the generation phase of the spreading code for each channel based on the phase difference information, the configuration of the broadcast receiving apparatus MS is not required. It has the advantage of being easy.

(Fifth Embodiment) In a fifth embodiment of the present invention, a terrestrial broadcasting station BC1,
The phase difference of each channel of the CDM broadcast signal arriving from the BC2 with respect to the reference phase of the spread code is detected, and the detected phase difference information is multiplexed with the CDM broadcast signal and transmitted to a terrestrial service area. Then, when the broadcast receiving apparatus MS selectively receives each channel of the CDM broadcast signal, the chip phase of the spread code is initialized based on the phase difference information received together with the CDM broadcast signal. The broadcast signal of each channel is selectively spectrum-despread and reproduced.

FIG. 7 shows a geostationary satellite S according to this embodiment.
FIG. 2 is a circuit block diagram illustrating a configuration of an AT. 3, the same parts as those in FIG. 3 are denoted by the same reference numerals, and detailed description is omitted.

C arriving from terrestrial broadcasting stations BC1 and BC2
The DM broadcast signal is received by a receiving antenna 51, then is subjected to low noise amplification in a receiving circuit 52, and is converted into an intermediate frequency signal. The received intermediate frequency signal is transmitted to each terrestrial broadcasting station B
The signals are distributed to correlators 61 to 6k provided corresponding to the total number of channels transmitted by C1 and BC2.

In these correlators 61 to 6k, the correlation between the received intermediate frequency signal and the spread code is obtained, and the correlation value is input to the control circuit 82. In the control circuit 82,
The phase difference between the orthogonal code generated by the geostationary satellite SAT and the received orthogonal code is detected based on the correlation values input from the correlators 61 to 6k for each channel. Then, information representing the detected phase difference for each channel is encoded and then input to the spread modulation circuit 58.

In the spread modulation circuit 58, the above-mentioned phase difference information is spectrum-spread by a spreading code, and the spread-processed phase difference information is input to a synthesis circuit 59. The combining circuit 59 combines the spread signal of the phase difference information with the CDM broadcast signal output from the receiving circuit 52. The CDM synthesized signal obtained by this synthesis is frequency-converted to an S-band frequency by a frequency conversion circuit 54 and further amplified to a predetermined transmission power level by a transmitter 55. Is transmitted to the service area on the ground.

As the broadcast receiving apparatus used in this embodiment, the same apparatus as that described in the third embodiment with reference to FIG. 5 can be used. With such a configuration, the CDM transmitted from the terrestrial broadcasting stations BC1 and BC2
When the signal is received by the geostationary satellite SAT, this geostationary satellite S
The AT detects the phase difference between the spreading code of each channel and the reference phase. Then, information representing the phase difference is multiplexed on the CDM signal and is notified to the broadcast receiving apparatus MS.

On the other hand, in the broadcast receiving apparatus MS, the phase difference information is separated and extracted from the CDM broadcast signal, the chip phase of the spreading code is initialized based on the phase difference information, and a desired channel is set by the spreading code. Is despread and reproduced.

Therefore, when the terrestrial broadcasting stations BC1 and BC2 transmit the broadcast signal of each channel by spreading the spectrum using a spread code, even if the spread signal is spread without synchronizing the spread code between the channels, the broadcast receiving apparatus MS
In addition to the above-mentioned CDM broadcast signal, terrestrial broadcast stations BC1, B
The chip phase of the spread code is initialized based on the phase difference information sent from C2, and the spread code causes the CDM broadcast signal to be spectrum despread. Therefore, compared with the case where synchronization is established by searching for a spreading code for each channel, spreading code synchronization with respect to each channel can be established in a short time, whereby channel switching can be performed with good responsiveness. Can be done to speed.

According to this embodiment, each terrestrial broadcasting station B
C1 and BC2 do not need to be provided with a circuit for detecting the phase difference between the spread codes of the respective channels and multiplexing the detected information, whereby each of the terrestrial broadcast stations BC1 and BC2
Can be simplified.

(Sixth Embodiment) In a sixth embodiment of the present invention, a phase difference of a spread code between CDM broadcast signals transmitted by a plurality of terrestrial broadcast stations BC1, BC2, and BC3 is detected by a geostationary satellite SAT. Then, a phase difference control signal for reducing the phase difference to zero is transmitted from the geostationary satellite SAT to each of the terrestrial broadcasting stations BC1, BC2, and BC3, which are the transmission sources. Then, in each of the terrestrial broadcasting stations BC1, BC2, and BC3, based on the notified phase difference information, the transmission timing of the broadcast signal to be transmitted by the own apparatus is variably controlled, whereby each of the terrestrial broadcasting stations BC1, BC1, and BC3 is controlled. BC2, BC
3 is such that the spread code phase difference of the CDM broadcast signal transmitted becomes zero on the geostationary satellite SAT.

FIG. 8 shows a geostationary satellite S according to this embodiment.
FIG. 2 is a circuit block diagram illustrating a configuration of an AT. In the figure, CDM broadcast signals transmitted from terrestrial broadcast stations BC1, BC2 and BC3 are received by a receiving antenna 111 and then amplified by a low noise amplifier 112. Then, the received CDM broadcast signal is frequency-converted from the Ku band to the S band by the frequency conversion circuit 113, and further amplified to a predetermined transmission power level by the transmission power amplifier 114. Is transmitted to the service area on the ground.

The received CDM broadcast signal output from the low-noise amplifier 112 is input to the receiving circuit 121, where it is frequency-converted into, for example, an intermediate frequency signal and then distributed and input to the correlators 131 to 13k. . The correlators 61 to 6k are provided by the number corresponding to the total number k of channels multiplexed by the terrestrial broadcasting stations BC1 and BC2.

In the correlators 61 to 6k, the correlation between the received intermediate frequency signal and the spread code is obtained, and the correlation value is input to the phase difference detection circuit 122. In the phase difference detection circuit 122, the correlators 61 to 6 are provided for each channel.
The phase difference between the spread code generated by the geostationary satellite SAT and the received spread code is detected based on the correlation value input from k. Then, a phase control signal for reducing the detected phase difference to zero is generated for each channel, and these phase control signals are respectively applied to modulation circuits (MOD) 141 to 14.
k.

In these modulation circuits 141 to 14k, primary modulation such as QPSK and spread spectrum modulation using respective spread codes for transmitting phase control signals are performed on the phase control signals. And these modulation circuits 14
The spread modulated signals output from 1 to 14k are
The signal is synthesized into a one-series signal at 23 and input to the transmitter 124 as a CDM phase control signal. The transmitter 124 performs a process of frequency-converting the CDM phase control signal into a Ku-band signal and a process of amplifying the frequency-converted Ku-band transmission signal to a predetermined transmission power level. Then, the Ku output from the transmitter 124 is output.
The band CDM phase control signal is transmitted from the Ku band transmission antenna 125 to the terrestrial broadcasting stations BC1 and BC2 as transmission sources via the Ku band downlink transmission path.

On the other hand, each of the terrestrial broadcasting stations BC1 and BC2 is configured as follows. FIG. 9 is a circuit block diagram showing the configuration of the transmission unit. In this figure, the same parts as those in FIG. 2 are denoted by the same reference numerals.

That is, the CDM phase difference control signal sent from the geostationary satellite SAT via the Ku-band downlink transmission path is input to the receiver 45 after being received by the receiving antenna 44, where it is amplified with low noise and the intermediate signal is output. The frequency is converted to a frequency signal. The received intermediate frequency signal is spectrally despread by a correlator 46 using a spread code for transmitting a phase control signal, and the received signal obtained by this is detected by a detector (DET) 47 by a detection method corresponding to the QPSK method. It is detected. Then, the reproduced phase control signal is input to the control circuit 48.

The control circuit 48 transmits the reproduced phase control signal to the spread code generator 2 of the corresponding channel.
1 to 2n. Each of the spreading code generators 21 to 2n corrects the generation start phase of the spreading code to the timing given by the phase control signal. Therefore, in the spread modulators 11 to 1n, the broadcast signals of the respective programs are spread spectrum by the spread codes whose generation timings are corrected by the spread code generators 21 to 2n.

The spread modulators 11 to 1n
The spread modulated signal of the broadcast signal output from the
The signal is synthesized into one series of signals by 1 and then input to the modulator 32. Then, after being modulated here, the transmitter 33 outputs Ku.
The signal is frequency-converted into a band transmission signal, further amplified to a predetermined transmission power level, and transmitted from the transmission antenna 34 to the geostationary satellite SAT.

With such a configuration, the geostationary satellite SA
At T, the phase difference of the spread code between the CDM broadcast signals transmitted from the terrestrial broadcast stations BC1, BC2, and BC3 is detected, and the phase control signal for making the phase difference zero is set to the CDM.
Multiplexed according to the system, and each terrestrial broadcasting station BC1,
It is transmitted to BC2 and BC3. On the other hand, each of the terrestrial broadcasting stations BC1, BC2, and BC3 controls the generation start timing of the spreading code of each channel in accordance with the phase control signal sent from the geostationary satellite SAT, so that the CDM transmitted by its own device is controlled. The transmission timing of the broadcast signal is delay-controlled.

Therefore, each of the terrestrial broadcasting stations BC1, BC
2, and the transmission of the CDM broadcast signal is started at a different timing from the BC3. For example, as shown in FIG. 10 (a), first, the terrestrial broadcasting station BC2 receives the channel CH11.
~ CH1n multiplexed CDM broadcast signal transmission starts,
Next, TD21 from the start of transmission of the terrestrial broadcasting station BC2
Terrestrial broadcasting station BC1 is channel CH
Transmission of a CDM broadcast signal multiplexed with 21 to CH2n is started. Further, at a time point delayed by TD23 from the transmission start time of the terrestrial broadcast station BC2, the terrestrial broadcast station BC3 starts transmitting a CDM broadcast signal multiplexed with the channels CH31 to CH3n.

Here, the delay amount of the transmission timing of each CDM broadcast signal is, as described above, the value of each terrestrial broadcast station BC.
The phase control signal sent from the geostationary satellite SAT is set so that the cross-correlation value of the CDM broadcast signal transmitted from the base station 1, BC2, and BC3 in the geostationary satellite SAT becomes zero. For this reason, each of the terrestrial broadcasting stations BC1, BC2,
The CDM broadcast signal transmitted from BC3 is a geostationary satellite SA
At T, the signal is received without any mutual phase difference as shown in FIG.

Accordingly, the broadcast receiving apparatus has a C code with spread code synchronization between the terrestrial broadcast stations BC1, BC2 and BC3.
A DM broadcast signal will be received. For this reason, in the broadcast receiving apparatus MS, the C received from any of the terrestrial broadcast stations is
As long as the spread code synchronization for the DM broadcast signal is established, the CDM broadcast from the desired terrestrial broadcast station can be performed simply by switching the spread code without re-establishing the spread code synchronization for the CDM broadcast signal coming from other terrestrial broadcast stations. Signals can be separated and reproduced. Therefore, when a receiving channel is switched from a CDM broadcasting signal transmitted by a certain terrestrial broadcasting station BC1 to a CDM broadcasting signal transmitted by another terrestrial broadcasting station BC2, the switching is performed at high speed with good responsiveness. Can be.

Further, by the phase control of the present embodiment, the spread code synchronization between a plurality of channels transmitted by the same terrestrial broadcast station is also established on the geostationary satellite SAT.
Even when S performs channel switching between a plurality of channels transmitted by the same terrestrial broadcasting station, switching can be performed in a very short time with high responsiveness only by switching to the corresponding spreading code.

(Other Embodiments) As another embodiment of the present invention, a broadcast receiver may be installed on a high-speed moving object such as an aircraft.

Generally, when an aircraft tries to receive a radio signal from a geostationary satellite SAT, the relative speed between the two is large, and a Doppler shift of the reception frequency occurs in the broadcast receiver of the aircraft. Conventional FDM method and TD
In a system using the M system, the bandwidth per channel is as narrow as, for example, about 10 KHz.
When a Doppler shift of about z occurs, it becomes extremely difficult to receive a desired channel. Therefore, various measures for correcting the above Doppler shift are required for an aircraft-mounted receiving device used in a system using the conventional FDM system or TDM system, and the device becomes large-scale.

However, in the satellite broadcasting system employing the CDM system as in the present invention, the broadcast signal of each channel is spread over a wide band of, for example, 25 MHz by a spread spectrum process. Therefore, even if a Doppler shift occurs in this state and the reception frequency shifts by about several KHz, the shift amount occupying the channel frequency band (25 MHz) becomes small, and the influence of the Doppler shift becomes negligible. For this reason, according to the present embodiment, it is possible to sufficiently use the broadcast receiving device mounted on an automobile or the like on land and used on an airplane as it is, thereby enabling airborne broadcast reception. The device can be made very small and inexpensive as compared with the conventional one.

The broadcast receiving apparatus used in the CDM satellite broadcasting system of the present invention can be mounted on other high-speed moving objects such as a bullet train. Also in this case, it is possible to perform high-quality reception with a small device ignoring the influence of the Doppler shift.

Further, when a broadcast receiving apparatus is mounted on a train, a so-called diversity receiving system is adopted, in which the length of the train is used, a receiving antenna is installed on a separate vehicle, and the respective received signals are combined. And this allows for even higher quality reception.

It should be noted that the present invention is not limited to the above embodiments, but includes procedures for establishing phase synchronization of spread codes and contents thereof, as well as configurations of a terrestrial broadcast station, a geostationary satellite, and a broadcast receiver. Various modifications are also possible.

[0077]

As described in detail above, according to the present invention,
The phase relationship of the spread code between the broadcast signals of the respective channels multiplexed by the multiplexing means is preset to a predetermined state by the synchronization means, or the multiplexing obtained by the multiplexing means by the phase difference detection means. Detecting the phase difference of the spread code between the channel signals of the converted broadcast signal, and notifying the broadcast receiving apparatus of information representing the phase difference between the spread codes detected by the phase difference detecting means by the notifying means. Accordingly, it is possible to provide a satellite broadcast system in which a channel of a multiplexed broadcast signal can be switched at a high speed with good responsiveness in a broadcast receiving device.

[Brief description of the drawings]

FIG. 1 is a schematic configuration diagram showing a first embodiment of a satellite broadcasting system according to the present invention.

FIG. 2 is a circuit block diagram illustrating a main configuration of a terrestrial broadcast station according to the first embodiment.

FIG. 3 is a circuit block diagram showing a configuration of a geostationary satellite according to a second embodiment of the present invention.

FIG. 4 is a circuit block diagram showing a main configuration of a terrestrial broadcast station according to a third embodiment of the present invention.

FIG. 5 is a circuit block diagram showing a configuration of a broadcast receiving device according to a third embodiment of the present invention.

FIG. 6 is a circuit block diagram showing a configuration of a geostationary satellite according to a fourth embodiment of the present invention.

FIG. 7 is a circuit block diagram showing a configuration of a geostationary satellite according to a fifth embodiment of the present invention.

FIG. 8 is a circuit block diagram showing a configuration of a geostationary satellite according to a sixth embodiment of the present invention.

FIG. 9 is a circuit block diagram showing a main configuration of a terrestrial broadcast station according to a sixth embodiment of the present invention.

FIG. 10 is a timing chart used to explain the operation of the sixth embodiment of the present invention.

[Explanation of symbols]

SAT geostationary satellites BC1, BC2, BC3 terrestrial broadcasting station MS broadcast receiver 11 to 1n, 43 spreading modulator 21 to 2n, 42 spreading code generator 31, 53, 59, 123 synthesis circuit 32 modulation Transmitters 33, 55 terrestrial broadcasting station Ku band transmission antennas 40, 48 terrestrial broadcasting station control circuit 41 phase difference information transmission circuit 44 terrestrial broadcasting station Ku band receiving antenna 45 ... Receivers 51, 111: Ku-band receiving antennas for geostationary satellites 52, 92, 121 ... Receiving circuits 54, 113 ... Frequency conversion circuits 56, 115 ... S-band transmitting antennas for geostationary satellites 46, 57, 61 to 6n, 93 , 94,131-13m
... Correlator 58,71-7n ... Modulation circuit 80,81,82 ... Control circuit of geostationary satellite 90 ... Control circuit of broadcast receiving apparatus 91 ... S-band receiving antenna of broadcast receiving apparatus 47,95,96 ... Detector ( DET) 97 operation unit 101 audio / video separation circuit 102 audio decoder 103 additional data decoder 104 video decoder 105 speaker 106 display 112 low noise amplifier 60, 114 transmission power amplifier 122 phase difference detection Circuits 141 to 14m: Modulator (MOD) 125: Ku-band transmitting antenna for geostationary satellite

 ──────────────────────────────────────────────────続 き Continuing on the front page (72) Inventor Nozomi Fujimori 1st location of Komukai Toshiba-cho, Saiwai-ku, Kawasaki-shi, Kanagawa Prefecture Inside the Toshiba Komukai Plant (72) Inventor Hideo Kikuchi Toshiba Komukai-shi, Kawasaki-shi, Kanagawa No. 1 town Inside the Toshiba Komukai Plant

Claims (7)

[Claims] 1. A satellite broadcast system for transmitting a broadcast signal of a plurality of channels from a terrestrial broadcast station, relaying the broadcast signal by a geostationary satellite, and broadcasting the broadcast signal to a broadcast receiving device located in a predetermined service area on the ground. The terrestrial broadcasting station includes: a multiplexing unit for performing code division multiplexing and transmission by spreading and combining the broadcast signals of the plurality of channels with different spreading codes for each channel, and code division multiplexing by the multiplexing unit. And a transmission synchronization unit for setting the phase relationship of the spread code between the broadcast signals of the respective channels to a predetermined synchronization state. 2. A satellite broadcast system for transmitting a broadcast signal of a plurality of channels from a terrestrial broadcast station, relaying the broadcast signal by a geostationary satellite, and broadcasting the broadcast signal to a broadcast receiving device located in a predetermined service area on the ground. The terrestrial broadcasting station includes multiplexing means for code-division multiplexing and transmitting the broadcast signals of the plurality of channels by respectively spreading and combining the spread signals with different spreading codes for each channel, and the geostationary satellite includes: Phase difference detecting means for receiving a code division multiplex broadcast signal transmitted from a broadcast station, and detecting a phase difference of a spread code between channels of the code division multiplex broadcast signal; and the received code division multiplex broadcast signal Setting the phase relationship of the spreading code between the respective channels to a predetermined synchronization state based on the detection result of the phase difference detecting means, Satellite broadcast system, characterized in that a transmission synchronization means for transmitting towards the service area. 3. A satellite broadcast system for transmitting a broadcast signal of a plurality of channels from a terrestrial broadcast station, relaying the broadcast signal by a geostationary satellite, and broadcasting the broadcast signal to a broadcast receiving apparatus located in a predetermined service area on the ground. The terrestrial broadcasting station is a multiplexing unit for code division multiplexing and transmitting by spreading and combining the broadcast signals of the plurality of channels with different spreading codes for each channel, and multiplexing is performed by the multiplexing unit. Phase difference information transmitting means for transmitting information indicating a phase difference of a spread code between broadcast signals of respective channels to the geostationary satellite, wherein the geostationary satellite receives the information indicating the phase difference. Phase difference information receiving means for performing the phase difference information between the channels of the received code division multiplex broadcast signal, the phase difference information A satellite broadcasting system comprising: transmission synchronization means for setting a predetermined synchronization state based on the information indicating the phase difference received by the broadcast reception means and transmitting it to the predetermined service area. 4. A satellite broadcast system for transmitting a broadcast signal of a plurality of channels from a terrestrial broadcast station, relaying the broadcast signal by a geostationary satellite, and broadcasting the broadcast signal to a broadcast receiving device existing in a predetermined service area on the ground. The terrestrial broadcasting station is a multiplexing unit for code division multiplexing and transmitting by spreading and combining the broadcast signals of the plurality of channels with different spreading codes for each channel, and multiplexing is performed by the multiplexing unit. Phase difference information transmitting means for transmitting information indicating the phase difference of the spread code between the broadcast signals of the respective channels to notify the broadcast receiving device, wherein the broadcast receiving device has information indicating the phase difference. Phase difference information receiving means for receiving the geosynchronous satellite based on the information indicating the phase difference received by the phase difference information receiving means. Receiving synchronization means for establishing spread code synchronization with respect to each channel of a code division multiplex broadcast signal received via the satellite broadcast system. 5. A satellite broadcast system for transmitting a broadcast signal of a plurality of channels from a terrestrial broadcast station, relaying the broadcast signal by a geostationary satellite, and broadcasting the broadcast signal to a broadcast receiving device existing in a predetermined terrestrial service area, The terrestrial broadcasting station includes multiplexing means for code-division multiplexing and transmitting the broadcast signals of the plurality of channels by respectively spreading and combining the spread signals with different spreading codes for each channel, and the geostationary satellite includes: A phase difference detecting means for receiving a code division multiplex broadcast signal transmitted from a broadcasting station, detecting a phase difference of a spread code between channels of the code division multiplex broadcast signal, and detecting the phase difference by the phase difference detection means. Phase difference information for transmitting information indicating the phase difference of the spread code between the broadcast signals of the respective channels to notify the broadcast receiving device. Communication means, the broadcast receiving apparatus comprises: a phase difference information receiving means for receiving the information indicating the phase difference; based on the information indicating the phase difference received by the phase difference information receiving means, A satellite broadcast system comprising: a reception synchronization unit for establishing spread code synchronization for each channel of a code division multiplex broadcast signal received via a geostationary satellite. 6. A satellite broadcasting a plurality of terrestrial broadcasting stations each transmitting at least one channel of broadcasting signals, relaying these broadcasting signals by geostationary satellites, and broadcasting to a broadcasting receiving device existing in a predetermined terrestrial service area. In the broadcasting system, each of the plurality of terrestrial broadcasting stations includes transmitting means for transmitting a broadcast signal transmitted by the own apparatus by spectrum spreading with a spread code different for each channel, and transmitting the geostationary satellite, Phase difference detection means for receiving a broadcast signal of each channel transmitted from the terrestrial broadcast station of each, and detecting a phase difference of a spread code between the broadcast signals of each of the channels, the plurality of received terrestrial broadcast stations And setting the phase relationship of the spread code between the channels of the broadcast signal from the predetermined synchronization state based on the detection result of the phase difference detection means. Satellite broadcast system, characterized in that a relay transmission synchronization means for transmitting toward a predetermined service area. 7. A plurality of terrestrial broadcasting stations each transmitting a broadcasting signal of at least one channel, and relaying these broadcasting signals by a geostationary satellite to broadcast to a broadcasting receiving device existing in a predetermined terrestrial service area. In the broadcasting system, each of the plurality of terrestrial broadcasting stations includes: a transmitting unit for spectrum-transmitting a broadcast signal transmitted by the own device with a spread code different for each channel and transmitting the broadcast signal; and a broadcast signal transmitted by the transmitting unit. Transmission timing control means for variably controlling the transmission timing of each channel, wherein the geosynchronous satellite receives the broadcast signals of each channel transmitted from the plurality of terrestrial broadcast stations, respectively, Phase difference detecting means for detecting a phase difference of a spread code between broadcast signals; and a phase difference detected by the phase difference detecting means. Is transmitted to each of the terrestrial broadcasting stations of the transmission source, and the transmission timing is set to the transmission timing so that the phase difference of the spread code between the broadcast signals of the respective channels transmitted by the terrestrial broadcasting stations becomes zero. A satellite broadcasting system, comprising: a phase difference information notifying unit variably controlled by a control unit.