JPH0423472B2 - - Google Patents

Description

[Detailed Description of the Invention] [Field of Industrial Application] The present invention relates to a satellite broadcast tuner for receiving television broadcasts by BS (Broadcast Satellite), and particularly relates to
MUSE (Multiple Sub-Nyquist Sampling
It can also be used for high-definition broadcasting using the Encoding (multiple subsampling transmission) method.

[Summary of the Invention] The present invention relates to a satellite broadcast tuner that receives high-definition broadcasting transmitted by the MUSE system using a broadcasting satellite (BS). It has been improved so that it can also be used as a conventional BS tuner.
In other words, the FM demodulator output of the BS tuner can be directly extracted separately, the time constant of the local oscillation AFC loop used for tuning can be switched and selected, and the audio D/A
By switching the converter input, it was possible to import the MUSE decoder's audio signal from outside.
This can be used to promote the spread of high-definition broadcasting in preparation for the upcoming high-vision broadcasting.

[Conventional technology] Figure 2 shows an example of a conventional BS tuner.

In Figure 2, 30 is a BS tuner, 31
32 is a video signal processing section, and 33 is an audio signal processing section. 1 is an input terminal, into which a BS-IF signal (1.3 GHz) obtained by frequency-converting the BS direct wave is input. 2 is a high frequency amplifier, 3
is a mixer, 4 is an intermediate frequency filter, 5 is an intermediate frequency amplifier, 6 is an AGC (automatic gain control amplifier), 7 is an amplitude limiter, 8 is an FM demodulator, 9 is an AFT (automatic frequency control circuit), 10 is a These are local oscillators, and these constitute the channel selection demodulation section 31.

11 is a de-emphasis circuit, 12 is an LPE (low pass filter), 13 is an energy spread signal removal circuit, and 14 is a video amplifier, which constitute the video signal processing section 32. 15 is a BPF (band pass filter), 16 is a 4-phase DPSK demodulator, and 17 is a PCM demodulator, and these constitute the audio signal processing section 33.

Reference numeral 18 denotes an RF modulator, which generates and outputs the same RF signal as terrestrial broadcasting (for example, channel 13) so that satellite broadcasting can be previewed even in a conventional television receiver. 19 is an output terminal that outputs the AGC voltage, 20 is an output terminal that outputs a video signal, 2
1 is an output terminal that outputs a bit stream, 22
A and 22B are output terminals that output audio signals;
23 is an output terminal that outputs an RF signal. 24
is the power supply, and 25 is the plug connected to AC100V.

The BS tuner 30 is a BS tuner added to the input terminal 1.
- Select a desired satellite broadcasting channel from among the IF signals by the channel selection demodulation section 31 and demodulate the FM,
The video signal processing unit 32 and the audio signal processing unit 33 output video and audio signals to the output terminal 2, respectively.
This is a device that is taken out to 0, 22A, 22B, etc.

[Problems to be Solved by the Invention] However, conventional BS tuners transmit and receive television signals in which video and audio signals are contained in the 6MHz band using broadcasting satellites, based on the current television standard system. It is configured to suit the purpose. Therefore, there is a problem in that a conventional BS tuner cannot be used as is for satellite broadcasting tuners when high-visibility signals using the MUSE system are transmitted, which require a band of 8 MHz or more. It was hot.

By the way, most of the components of the tuner you want to use for high-definition broadcasting are the same as conventional BS tuners, and it is rather simple in terms of functionality, so it is more economical to use it for both purposes. It is expected that its spread will be accelerated once it is launched.

In other words, the following are the components that can be used for both purposes so that there is no need to install them twice.

(1) All RF (radio frequency) and IF (intermediate frequency) systems (2) Audio D/A conversion circuit, output filter, amplifier, etc. (3) FM demodulation system Also, audio D/A in item (2) By sharing the components after conversion, it is possible to cancel the noise generated when switching between conventional television and high-vision by applying appropriate mute.

SUMMARY OF THE INVENTION An object of the present invention is to solve the above-mentioned problems and provide a satellite broadcast tuner that can switch and receive both conventional television and high-vision (MUSE system) in good condition. be.

[Means for Solving the Problems] In order to achieve such an object, the present invention provides, for example, a conventional BS tuner that
The FM demodulated signal can be taken out directly, the time constant of the local oscillation AFC loop used for tuning can be switched and selected, and the audio D/A conversion input can be switched to import it from the outside. Do it like this.

That is, the present invention provides a means for receiving television broadcast radio waves by a broadcasting satellite, and a means for receiving radio waves for television broadcasting by a broadcasting satellite.
means having an AFC loop and selecting the received signal to perform FM demodulation; means for extracting a video signal from the FM demodulated signal; and means for decoding a digital audio signal from the FM demodulated signal;
In a satellite broadcasting tuner having means for D/A converting the digital audio signal and extracting the audio signal, the extracting means directly extracts the FM demodulated signal, and the specifying means for specifying the time constant of the AFC loop for local oscillation. and a switching means for switching the input so that the input to the D/A conversion means can be taken in from the outside instead of a digital audio signal.

[Operation] According to the present invention, a signal in a band of 8.1 MHz or more based on the MUSE system can be extracted as it is and supplied to the MUSE decoder. In addition, keyed AFC that matches the peak clamp using the MUSE method
This allows the local oscillator to be controlled and stable reception to be achieved. Furthermore, audio can be taken in from the MUSE decoder, and the audio D/A conversion circuit, output filter, and amplifier can be used as is.

[Example] Hereinafter, the present invention will be described in detail with reference to the drawings.

FIG. 1 is a block diagram showing the configuration of one embodiment of the present invention.

In FIG. 1, parts similar to those in FIG. 2 are given the same reference numerals, and their explanations will be omitted.

Reference numeral 50 denotes a satellite broadcast tuner, which is capable of tuning and demodulating both conventional television and high-definition television transmitted by the MUSE system. 51 is a MUSE decoder, 51A is an output terminal that outputs a video signal, 51B is an output terminal that outputs an audio signal, and 51K is an output terminal that outputs a key signal.

52 is an FM demodulator, which includes the intermediate frequency filter 4, intermediate frequency amplifier 5, and the intermediate frequency amplifier 5 shown in FIG.
AGC6, amplitude limiter 7, FM demodulator 8 and
Consists of AFT9. 53 is a video amplifier;
The output of the FM demodulator 52 is directly amplified. 54 is an output terminal, from which the output of the video amplifier 53 is taken out. 55 is an audio trap filter, 5.7M
Suppresses Hz audio modulation waves.

56 is an audio decoder that demodulates the audio PCM signal. 57 is a D/A converter,
Converts PCM signals to analog audio signals. 57
S is a switch for changing the input of the D/A converter 57, 58 is an audio amplifier, and 59 is an audio output terminal.

60 is an input terminal, and MUSE decoder 51
Input the audio signal from. 61 is an output terminal from which the output of the audio decoder 56 is taken out. Switches 62 and 63 select the time constant of the AFC operation from the FM demodulator 52.

64 is an AND circuit, 65 is a retriggerable multi,
66 is an input terminal for inputting a key signal for selecting an AFC time constant.

Next, the operation of the main components of this embodiment will be explained with reference to FIG.

Although various embodiments are possible, the most typical one is shown in this example. It may also be practical to remove some of the functions shown here.

The part indicated by the thick line in Figure 1 is the high-definition system using the MUSE system (hereinafter referred to as MUSE) and the conventional television system using the NTSC system (hereinafter referred to as ``MUSE'').
This is a part added to the conventional BS tuner to make it functional for both NTSC and NTSC.

An output terminal 54 is provided to directly output the video signal output from the FM demodulator 52 and not passed through the audio trap filter 55.
Connected to MUSE decoder 51.

Regarding the AFC loop, in the case of NTSC,
Average value AFC is used and switch 63
is selected and the AFC loop is closed. MUSE
In this case, keyed AFC is used to clamp the clamping level specific to MUSE, and switch 6
2 is selected and the AFC loop is closed. In this embodiment, when the key signal is input from the output terminal 51K of the MUSE decoder 51 to the input terminal 66, Switch 62 is selected to close AFC. If the key signal for AFC selection is not input here, the retriggerable multi 65
The output becomes "H", the switch 63 is selected, and the average value AFC loop is closed.

In this embodiment, an AND circuit 64 is provided so that when there is no key signal, it does not matter whether the key signal is at the "H" level or the "L" level.
If a pull-down or other failure occurs and the AFC key signal input terminal 66 is not connected, it will always be “L” and the AFC selection key signal output from the MUSE decoder 51 will be
This AND circuit 64 is unnecessary if it is guaranteed that the output will always be "L" when there is no input.

In this embodiment, AFC selection is performed using the AFC selection key signal.
When the time constant circuit of the switch 62 is closed and the switch 62 is closed, the same signal is used to control the switch 67, and the audio signal is switched to the audio signal from the MUSE decoder 51 and input to the D/A converter 57. . The reason for switching the audio here is MUSE
This is because it is desired to automatically switch the respective audio signals between NTSC and NTSC, and also because components such as the D/A converter 57 and the audio amplifier 58 are to be shared. In this case, the audio signal is transferred using AES, for example.
(AUDIO ENGINEERING SOCIETY)/EBU
(European Broadcasting Federation) method should be used.

When controlling with the above method, MUSE
The AFC key signal from the decoder 51 is sent to MUSE
It is necessary to kill it when a signal other than that is received, that is, when the MUSE is out of synchronization lock. Instead of doing this, a method is proposed in which a switching signal is applied from outside the tuner to switch the switches 62 and 63 that select the AFC time constant circuit, and the switch 67 that selects the input signal of the audio D/A converter 57. It can also be considered.

Considering that MUSE/NTSC dual-purpose receivers will be available in the future, it will be necessary to not only extract the MUSE output directly from the FM demodulator 52, but also to
When receiving signals other than MUSE, it may be convenient to configure the system so that the same signal as the NTSC signal is obtained and output.

[Effects of the Invention] As is clear from the above, according to the present invention,
When MUSE and NTSC satellite broadcasts are performed in parallel, they can be easily received with a single satellite tuner.

Furthermore, when receiving a program with mixed MUSE/NTSC programming, it is possible to view the program with automatic switching depending on the content of the modulated signal.

Furthermore, it is economically effective, and by disseminating this type of satellite broadcasting tuner in advance, it is expected that it will be possible to smooth the transition to the reception of high-definition broadcasting using the MUSE method. can.

[Brief explanation of drawings]

FIG. 1 is a block diagram showing the configuration of an embodiment of the present invention, and FIG. 2 is a block diagram showing the configuration of a conventional example. 1, 60, 66...Input terminal, 2...High frequency amplifier, 3...Mixer, 4...Intermediate frequency filter,
5... Intermediate frequency amplifier, 6... AGC, 7... Amplitude limiter, 8, 52... FM demodulator, 9...
AFT, 10... Local oscillator, 11... De-emphasis, 12... LPE, 13... Energy spread signal removal circuit, 14, 53... Video amplifier, 1
5...BPF, 16...4-phase DPSK demodulator, 17...
...PCM demodulator, 18...RF modulator, 19,2
0, 21, 22A, 22B, 23, 54, 59,
61... Output terminal, 24... Power supply, 25... Plug, 30... BS tuner, 31... Tuning/demodulation section, 32... Video signal processing section, 33... Audio signal processing section, 50... Satellite broadcast tuner, 51
...MUSE decoder, 55...Audio trap filter, 56...Audio decoder, 57...D/A
Converter, 57S, 62, 63...Switch, 58
...Audio amplifier, 64...AND circuit, 65...
Retriggerable multi.

Claims (1)

[Scope of Claims] 1. Means for receiving television broadcast radio waves from a broadcasting satellite, means having an AFC loop for local oscillation, and means for selecting and FM demodulating the received signal, and the FM demodulated signal. A satellite broadcasting tuner comprising: means for extracting a video signal from the FM demodulated signal; means for decoding a digital audio signal from the FM demodulated signal; and means for D/A converting the digital audio signal to extract an audio signal. an extraction means for directly extracting the FM demodulated signal; a specification means for specifying the time constant of the AFC loop for local oscillation; and an input to the D/A conversion means can be input from the outside instead of the digital audio signal. A tuner for satellite broadcasting, comprising a switching means for switching inputs as shown in FIG. 2. The tuner for satellite broadcasting according to claim 1, wherein the specifying means specifies the time constant of the AFC loop using a key signal given from the outside. 3. The tuner for satellite broadcasting according to claim 2, wherein the switching means switches so as to receive input from the outside in response to the key signal. 4. The tuner for satellite broadcasting according to claim 2, wherein when the key signal does not arrive for a long time, the specifying means specifies the AFC loop as a scheduled time constant. . 5. The tuner for satellite broadcasting according to any one of claims 1 to 4, wherein the specifying means specifies the time constant by an external control signal. Chuyuna. 6. In the satellite broadcasting tuner according to any one of claims 1 to 5,
A tuner for satellite broadcasting, wherein the switching means switches the input based on an external control signal. 7. In the satellite broadcasting tuner according to any one of claims 1 to 6, the specifying means specifies a time constant of an AFC loop for local oscillation used in each of the MUSE system and the NTSC system. A tuner for satellite broadcasting characterized by specifying.