JPS59211380A - Community receiving system of satelite broadcasting - Google Patents

Abstract

PURPOSE:To decrease the loss of signals by making a sound PSK subcarrier and a sound FM subcarrier to be subjected to frequency division multiplex to a VBS- AM signal. CONSTITUTION:A receiving antenna 11 of a head end section A receives a satellite broadcast television signal, the section A converts the signal into an intermediate frequency signal and then distrubutes and applies the result to a converter 14. The converter 14 converts the intermediate frequency signal to a VBS- AM signal at each channel and outputs the VBS-AM signal while applying two sound subcarriers of PSK and FM to the signal with frequency division multiplex. The signal multiplexed at each channel is mixed at a mixer 15, and transmitted to a receiving terminal device C via a distributor/branching filter 19 or the like. The receiving terminal device selects a channel from the received multiplex signal and outputs the VBS-AM signal where the sound FM subcarrier is multiplexed and demodulates a sound signal from the sound PSK subcarrier.

Description

[Detailed Description of the Invention] [Technical Field of the Invention] This invention relates to a satellite broadcasting system that receives satellite broadcasting television signals using a common antenna and distributes them to receiving terminals via a coaxial cable or the like. Regarding the system.

[Technical background of the invention and its problems]

The satellite broadcasting system uses the broadcasting station J'11 located in a geostationary orbit approximately 35,800 km above the equator to directly broadcast television signals transmitted from the earth station to general viewers (each home, joint receiver). It is something to do. Not only can you get high-quality video and audio without interference, you can also get a channel separate from the terrestrial channel, making it possible to broadcast nationwide. In the future, satellite broadcasting is also considered as a broadcasting medium for new types of broadcasting services, such as teletegist, audio-only broadcasting, and high-definition TV, and is expected to become the core of so-called knee media.

television? Digitalization of the audio signal transmission method for TJ Star Broadcasting is being considered, and adoption is being considered in countries around the world. Japan has decided to be the first in the world to digitize the audio signal transmission method for television broadcasting, and plans to implement this from Satellite Broadcasting No. 2 (BS~2). By digitizing the audio signal transmission method, you can enjoy corner-quality audio on broadcasts just like with digital audio discs, etc., and you can also multiplex audio broadcasts other than TV audio, and use extra transmission bits for facsimile or It can be used for other multiplex broadcasts such as still images, etc.
Enables transmission that can respond to the diversification of the information society 3.
The audio signal transmission method that Japan and many other countries are trying to adopt is called the "audio PCM subcarrier method."
As shown in FIG. 1, the audio subcarrier frequency-division multiplexed to the video signal 1, ? (5,7272727vIHz) to PC
4-phase differential phase modulation with M-encoded audio signal [hereinafter referred to as 4-phase 1
) PSK (Differential Phase S
This is a method called ``hiftKeying''.

As a method for PCM encoding and multiplexing audio signals,
The transmission specifications are as shown in the table below.

In other words, there are two transmission modes, A and B. Mode A has an audio signal bandwidth of 15 kHz (sampling frequency of 32 kHz, number of child pits of 14).
/10-bit quasi-instantaneous companding) audio channel to 4'f
B mode has an audio signal bandwidth of 20
It has two audio channels of kHz (sampling frequency 48 kHz, number of stitching bits 16 bits). Furthermore, both the A and B modes have over 161 independent data bits that can be used for data transmission such as facsimile. In order to receive and reproduce the sound of the Kungseon Broadcasting Television signal using such an audio signal transmission system, a PSK demodulation circuit and a PCM signal processing circuit are required in the SHF reception system for satellite broadcasting. That is, in the SHF receiver for satellite broadcasting, first, the FM demodulator
The baseband video signal and the audio subcarrier (5,727272MHz) PSK-modulated with the PCM audio signal are demodulated, but the audio subcarrier has a bandwidth of about I
The signal is extracted with a MHz bandpass filter and fed to a PSK tuner circuit. A PCM audio signal is obtained by the phase synchronized detection method in the PSKi modulation circuit. Next, through PCM signal processing such as dinterleaving, error correction, and correction, the analog audio signal is restored by the l)/A converter.

The method of receiving satellite broadcast television signals is to install a 1.1゛ SHF receiver for single-star broadcasting in the valley, and use the 1-individual reception method to directly receive radio waves from satellites individually.
There is a ``community reception method'' in which a communal reception device is installed and the output signal is distributed to each household. Of course, individual reception refers to reception by simple household equipment, especially equipment having a small antenna, and joint reception refers to reception by a receiving device having a larger common antenna than individual reception.

Currently, approximately 3 million households subscribe to CATV in Japan, but there are also a considerable number of communal reception facilities in apartment complexes such as Ahart and condominiums, and a considerable number of subscriber households are connected to the coaxial cables of these facilities. There are only a few TV receivers available. In order to popularize satellite broadcasting,
It is necessary to make it possible for recipients of these existing CATV facilities to receive satellite broadcasting. 1, I'm afraid this will continue to develop in the future! /[It is necessary to introduce the joint reception (iLi system) to the existing CATV facility, which can receive I+G broadcasting.

Even in private homes other than CATV subscribers, shared use of receiving antennas is economical and windproof.

Defense 1. Due to the difficulty of installation a6, there are many cases where it is better to share the receiving antenna and receive joint reception3.Furthermore, in areas with low surface power flux density,
Similar to terrestrial broadcasting, new joint reception facilities will need to be built.

Even in the overcrowded residential area of IS city, aesthetically,
Furthermore, from the viewpoint of installation location constraints, there may be cases where it is appropriate to receive satellite broadcasting in the form of joint reception.

When configuring a joint reception system that can receive satellite broadcasts in this way, a method for transmitting satellite broadcast television signals over a coaxial cable is a method (1) in which satellite broadcast television signals are transmitted as FM signals. A possible method (2) is to convert the signal into a vestigial side fluorescent signal (VSB-AM) signal and transmit it, which is the same as terrestrial television broadcasting. Method (1) is: 12 GHz received by the Gurabora antenna
Either convert satellite broadcast radio waves in the I GHz band to intermediate frequency signals in the I GHz band and transmit them as is, or convert them into VHF band or U
The advantage of this method is that it can transmit satellite broadcast signals, especially their audio subcarrier signals, while maintaining high quality. However, in order to do this, the transmission frequency must be set to a high frequency in the I GHz band or UHF band, which causes a lot of transmission loss.
There are limits to the transmission distance and number of distribution terminals, and the disadvantage is that the system cannot be enlarged. Therefore, it is not suitable for large-scale housing complexes.

Furthermore, in order to transmit the B channel of satellite broadcasting allocated to Japan, a wide frequency bandwidth of 300 MHz is required, and nine performance conditions required of the transmission path and transmission equipment become extremely strict.

Based on this, method (2) converts the 12 GHz band satellite broadcast radio waves received by a parabolic antenna into an IGH2 band intermediate frequency signal, demodulates the baseband video and audio signals, and then This is a method that converts (remodulates) the signal into a VSB7AM signal, which is the same as terrestrial television broadcasting in the VHF band or UHF band, and transmits it. In this case, the additional device at the subscriber's home will be Nenjo. However, if a mid-band channel or Sunoya channel is used as the transmission channel, convergence is required. The feature of this method is that Tljj can be simply transmitted using existing transmission equipment.

However, after demodulating the satellite broadcast radio waves, they are remodulated into a signal similar to terrestrial TV broadcasting, so they are transmitted as FM signals (1)
Unlike the above method, audio signal transmission is limited to two channels using the conventional audio multiplex modulation method, and the backdoor signal bandwidth is 15 kHz or less (limited by the transmission specifications of the audio multiplex modulation method). Therefore, the information on the satellite broadcast audio channel is not completely transmitted, and the quality is the same as that of conventional television broadcasting. In other words, the benefits of television satellite broadcasting are not fully utilized.

[Purpose of the invention]

An object of the present invention is to provide a satellite broadcasting joint reception system that enables joint reception of high quality and without loss of information with a relatively simple facility configuration and not demanding performance requirements.

[Women are the inventors]

This invention converts a received satellite broadcast television signal into a VSB-AM @ code for each channel, and also converts the received satellite broadcast television signal into a VSB-AM @ signal and demodulates the audio PSK1ii11 from this television signal.
The above VSB-
Required replacement for frequency division multiplexing of AM signals is provided, and the multiplexed signals obtained from each of these conversion devices are transmitted to the receiving terminal equipment via a transmission path including a coaxial cable, etc., and the receiving terminal equipment converts the received multiplexed signal to the received multiplexed signal. After selecting the desired channel signal, the VSB-AM signal multiplexed with the audio FM subcarrier is output, and the audio signal is demodulated from the audio PSK subcarrier! There is one symptom.

〔Effect of the invention〕

According to this invention, unlike the method of transmitting a satellite broadcast television signal in the form of an FM signal to a receiving terminal device, neither the VSB-AM signal nor the audio subcarrier signal is accompanied by a large loss. In transmission, the performance conditions required for facilities such as transmission lines and various transmission equipment have been relaxed.
Existing equipment is available and can be used for iJl. Even in the case of new construction, the technical and economic burden can be kept to a minimum of one person.

Furthermore, regarding audio subcarriers, P
Since the SK subcarrier is also transmitted at the same time, it is possible to reproduce the information of all -i voice channels and also to generate high quality voice by PCM. It is also of course possible to extract independent data bits.

[Output side of invention]

FIG. 2 schematically shows the structure of a satellite joint reception system according to an embodiment of the present invention, which is roughly divided into a head end section A, a transmission path B, and a receiving terminal device C. .

In the head end section A, a 12 Gl (Z band (SHF) satellite broadcast television signal is received by a receiving antenna such as Noyara Bora 1, and after being amplified by a low noise amplifier in an outdoor unit and a tonneau 2, approximately I Convert to a GHz intermediate frequency signal (FM signal).

This intermediate frequency signal is distributed by a distributor 13 to a converter 14 installed for each channel.

The conversion device 14 converts the intermediate frequency signal from the distributor 13 into a VSB-AM signal for each channel, and 17
) Two audio subcarriers, PSK and FM, are frequency-division multiplexed onto a VSB-AM signal and output, and is configured as shown in FIG. 3, for example.

The conversion device 14 in FIG. 3 is roughly divided into an FM-AM converter 31 and a remodulation device ss.
A specific channel (or channel) determined for each switching device 14 by the cheese circuit 32 in the M-AM converter 3
is selected, and the baseband video signal and audio signal (PSK) are tuned by the limiter/FM post-adjuster 33. The sound JM numbers are further decoded by a KPSI (rear leg/PCM decoder 34), and baseband N voice signals for two channels are restored.

The baseband video 41A obtained by the FM-AM converter 3) is converted into VSB A fVl 4B in the 50 MHz band by the IF enhancer 36 in the remodulation device 35. At this time, the %IFF modulator 36 is supplied with the PSK subcarrier modulated by the limiter/'FM*:# unit 32, and the audio demodulated by the PSK demodulator/PCM decoder 34. The sound p F M g++ hv modulated by the FMi signal is supplied from the audio multiplier 37, and these two audio subcarriers are frequency division multiplexed onto the VSB-AM signal.

The output of this IF modulator 36 is converted into, for example, a mid-band signal by a frequency converter 38.

The frequency spectrum of the mid-band multiplexed signal thus obtained by the remodulation device 935 is shown in FIG.

41 is a video signal consisting of a VSB-AM signal, and an audio FM subcarrier 4 is placed 4.5 MHz above the video carrier.
2, and an audio PSK subcarrier is placed further above 1.3 MHz. In addition, 41' is the VS of the instantaneous connection channel.
B - A M signal is shown.

As shown in FIG. 4, the audio PSK subcarrier and the audio F
The occupied bandwidth of the signal in which the M subcarriers are multiplexed into the VSB-AM signal is 8 MHz (the audio PSK subcarrier is 5 MHz).
8 MHz) or 7,5 MHz
z (if the audio PSK subcarrier remains at 5.727272 MHz). Therefore, it is not preferable to transmit in the V) IF low band and high band that are mixed with the conventional terrestrial TV channel (6MHz bandwidth), and it is recommended to redistribute the mid-band dedicated to cable transmission and transmit it. desirable.

FIG. 5 shows an example of channel allocation when the multiplexed signal shown in FIG. 4 is transmitted in the mid-band.

In Figure 5, ■, ■, ■ indicate low band channels of terrestrial television broadcasting, ■... indicate high band channels, and σ, yaku, and o' indicate local oscillation frequencies corresponding to channels ■, ■, ■. show.

The symbol ma indicates the position of the video carrier wave of the mid-band terrestrial cable broadcasting, and the ma represents the position that matches the video carrier wave of the multiplexed signal. 01
' Become capable.

As mentioned above, the audio signal in the television satellite broadcasting that is planned to be implemented in Japan will be divided into two modes, A and B, and the audio bandwidth in A mode will be 15]<Hy.

audio signals are transmitted through four channels. If only audio FM subcarriers are used, similar to audio multiplexing in current TV broadcasting, out of these four channels, the first and second audio channels (stereo or bilingual) are TV audio. Only the third one can be transmitted. The fourth audio channel and independent data bits cannot be transmitted. Also, B
In this mode, the audio signals are only two channels for television, but the audio bandwidth is 20 kHz, and transmission using only audio FM subcarriers has an audio bandwidth of 15 kHz, so good transmission cannot be achieved. Of course, independent data bits in B mode cannot be transmitted either. However, if the present invention further uses voice PSK subcarriers for transmission, it becomes possible to transmit fJ3, eiλ4 voice channels and independent data bits in A mode, and 2 in B mode.
High quality transmission of the channel's audio signal and independent data bits can be made possible.

The multiplexed signal consisting of the VSB-AM signal of each channel m and one audio subcarrier of FM and PSK obtained by the converter 14 in this way is guided to the transmission line B as shown in FIG. , all channels are mixed in the mixer 17, and then transmitted to the receiving terminal device C via the coaxial cable 16, the amplifier 17, the divider/brancher 18, etc.

The receiving terminal device C consists of an indoor unit 20, a television receiver 21, an audio device 22, an additional information processor 23, etc., which are appropriately connected to the indoor unit 20.

The indoor unit 20 is configured, for example, as shown in FIG.
The lj conversion signal 60 is manually inputted to the lj 1 circuit 61,
The channel selection device 62 selects a signal of a desired channel, and the selected signal is, for example, in the frequency band of the 13th channel of the UHF band (center frequency 473λIII
−Iz). The output of this tuner circuit 6 is transmitted through a bandpass filter (B
PF) 63, and the audio PSK subcarrier component is removed. Since the output signal of this BPF" 63 has the same format as current television broadcasting, it can be received through the antenna end of the television receiver 2.

At this time, the TV signal on the 13th channel contains two audio signals.
Since the channels are multiplied by the TV audio system and the multiplexing is ft, the sound can be reproduced using the TV's built-in speakers.

The reasons for converting the VSB-AM signal into the frequency band of channels 1 and 3 in this way are as follows: (1) Since adjacent channels are far apart, there is less streaky interference.

■ The frequency band of the 13th channel is not currently used, and it is expected that it will not be used for the time being even after Si+.

■ Home VTRs can be connected to 7ζ or rain broadcast receivers that use the 41 or 2nd channel without any problems.

etc. are listed.

The output of the tuner circuit 61 is further detected by a wave detector 64, and transmitted through a BPF 65 to an audio PSK subcarrier (5, s
Ml (Z or 5.727272 MHz) is extracted.

The output of this BPF 65 is supplied to a PSK q counterclaim/PCM decoder 66. An analog audio signal is extracted from the PSK demodulator/PCM decoder 66 and supplied to the audio device 22 . In addition, since the entire pit stream after error correction and correction can be taken out from the PCM IB processing section in the PSK post-tone/PCM decoder 66, the independent data bits can be sent to a detailed information processing device 22 such as a facsimile machine.
can be supplied to

[Brief explanation of drawings]

Figure 2 shows an embodiment of the present invention. Schematic configuration of the Great Engineering Star Broadcasting Cooperative Bunkaku System[/1, atλ31-1 is a diagram showing an example of the converter's book, 4th C1 shows the information transmitted from the converter +'7 to the receiving terminal device Jl. Figure 5 shows an example of channel allocation when transmitting this multiplexed signal in the mid-band, and Figure 6 shows the frequency spectrum of the multiplexed 1♂-H,). It is a diagram showing the configuration file of A...Head end, B...Transmission path, C...Reception m.
yiM terminal device, 11... Antenna, 14... Conversion device, 16... Coaxial pull, 20... Indoor unit, 3... F'M,/AM converter, 35
・・Re-gun-sho loading box, 6 pieces... Cheesy circuit, 62...
Prediction device, 63°65...Band pass filter, 6
4...Detector, 66-PSK demodulation/PCM decoder. Departing IA; fj representative patent attorney Takeshi Suzue Examination 1st
Figure 3 Figure 3 (

Claims (3)

[Claims] (1) In a joint reception system for a satellite broadcast television signal in which an audio subcarrier PSK-modulated with a PCM audio signal is frequency-division multiplexed onto a video signal, the television signal is converted to a VSB-AM signal for each channel, and Audio PS demodulated from this television signal
The above VS
A conversion device that performs frequency division multiplexing on the B-AM signal, a transmission path that transmits the multiplexed signals obtained by each of these conversion devices, and a signal of a desired channel from the multiplexed signal transmitted via this transmission path. What is claimed is: 1. A satellite broadcasting joint reception system comprising: a reception terminal device which selects a channel and outputs a VSB-AM signal multiplexed with the audio FM subcarrier, and demodulates an audio signal from the audio PSK subcarrier. (2) The conversion device converts audio PfSK subcarriers and audio F
The satellite broadcasting joint reception system according to claim 1, wherein the M sub-1 transmission wave converts a frequency division multiplexed VSB-AM signal into a Mitsutonondo signal and outputs the converted signal. . (3) The receiving terminal device is a patented broadcasting joint reception system characterized in that the receiving terminal device converts the VSB AM (number i) into the <y number of a specific television channel and outputs the multiplexed audio FM subcarrier. .