JPH066694A - Satellite broadcast receiving device - Google Patents

Abstract

PURPOSE:To provide the satellite broadcast receiving device which excellently mutes an image and an audio when a television broadcast signal other than a channel which is permitted as a CS broadcast is received. CONSTITUTION:The base band signal SBS outputted from an FM demodulating circuit (not shown in figure) is supplied to a QPSK demodulating circuit 3 through a BPF 2 and the I/Q signal which is demodulated by the demodulating circuit 3 is supplied to a PCM decoder 4. The PCM decoder 4 detects the state of the C7 bit ('1' at the time of the CS broadcast) in the PCM audio data and supplies the detection signal SD1 to an OR circuit 8. Further, the SBS is supplied to a detecting circuit 6 through a BPF 5, and the signal extracted by the BPF 5 is converted into a DC value, which is supplied to a voltage comparator 7 and compared with a reference level. The detection signal SD2 of the carrier of the PCM audio signal is obtained by the voltage comparator 7 and then supplied to an OR circuit 8. The image and audio are muted according to the output of the OR circuit 8.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a satellite broadcast receiver suitable for use in receiving broadcast waves from a communication satellite (CS).

[0002]

2. Description of the Related Art Broadcast radio waves from a communication satellite include a channel (CS broadcast) for which individual reception is permitted and a channel (CS communication) for which personal reception is not permitted. It is necessary for a CS broadcast receiving apparatus that will become popular in the future to have a function such that a CS communication channel cannot be received.

[0003]

If the signal has a carrier of PCM modulation, by demodulating this PCM signal, it is possible to determine whether or not it is a CS broadcast by a bit called C7 in the data area. FIG. 7 shows the configuration of a known PCM data frame, and when the C7 bit of the control signal is "1", it can be determined that it is CS broadcasting.

However, since a television broadcast signal without a carrier of PCM modulation is also transmitted as a channel approved for CS communication, such a signal is also accurately determined as a channel that must be muted, and the video is And voice muting must be done.

[0005] Therefore, an object of the present invention is to provide a satellite broadcast receiving apparatus that can perform a good muting operation of video and audio when receiving a television broadcast signal other than a channel approved as a CS broadcast. It is what

[0006]

The invention according to claim 1 is
It is provided with a detection means for detecting data included in the PCM audio data to determine whether or not the broadcast is a CS broadcast, and mutes at least one of video and audio based on the detection output of the detection means.

According to a second aspect of the present invention, there is provided a first detecting means for detecting data included in the PCM audio data for determining whether or not the CS broadcast is present, and a second detecting means for detecting a carrier of the PCM audio signal. And muting at least one of video and audio based on the detection outputs of the first and second detecting means.

According to a third aspect of the present invention, there is provided a first detecting means for detecting data included in the PCM audio data for determining whether or not the CS broadcast is present, and a second detecting means for detecting a lock state to the QPSK carrier. And muting at least one of video and audio based on the detection outputs of the first and second detecting means.

According to a fourth aspect of the present invention, there is provided a first detecting means for detecting data included in the PCM audio data to determine whether or not the CS broadcast is present, and a second detecting means for detecting a sync signal in the PCM audio data. And muting at least one of video and audio based on the detection outputs of the first and second detecting means.

[0010]

The bit called C7 in the PCM audio data is "1" in the case of CS broadcasting. According to the first aspect of the present invention, for example, video and audio are muted when the above-mentioned C7 bit is not "1".

By the way, all channels currently approved as CS broadcasting have PCM audio signals, but television broadcasting signals having FM audio signals are also transmitted from the same communication satellite. When it has an FM audio signal, it is naturally impossible to discriminate by the C7 bit in the PCM audio data described above.

As described above, since all channels approved as current CS broadcasts employ a system using PCM voice, a carrier of a PCM signal is detected when the channel is a CS broadcast. In the invention according to claim 2, for example, even if the above-mentioned C7 bit is "1", P
When the carrier of the CM audio signal is not detected, the video and audio are muted.

Further, as described above, since all the channels approved as the current CS broadcasting use the system based on PCM voice, when the broadcasting is CS broadcasting, QP is applied.
The lock on the SK carrier is detected. According to the third aspect of the present invention, for example, even if the bit of C7 is "1", video and audio are muted when the lock state to the QPSK carrier is not detected.

Further, as described above, since all the channels approved as the current CS broadcast use the PCM audio system, when the CS broadcast is used, the PC is not used.
The sync signal in the M audio data is detected. According to the fourth aspect of the invention, even if the above-mentioned C7 bit is "1", for example, the video or audio is muted when the sync signal in the PCM audio data is not detected.

[0015]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS An embodiment of the present invention will be described below with reference to the drawings. There are two types of television broadcast signals transmitted by a communication satellite (CS), which will be described first.

FIG. 5 shows the frequency allocation of the first system, and the frequency allocation is almost the same as that of the television broadcasting signal by the existing broadcasting satellite.
That is, a video signal of 4.5 MHz band and 5.727
QPSK-modulated P with 272 MHz carrier
It is composed of a CM audio signal. All of the channels (6 channels) licensed for CS broadcasting use the television broadcasting signal according to the first system.

FIG. 6 shows the frequency allocation of the second method. Although the bands of the television broadcast signal and the video signal by the current broadcasting satellite are the same, the frequency band is not PCM audio signal but 5 to 8.5 MHz. It is configured with FM audio signals with carriers in between. The television broadcasting signal according to the second system is used in a broadcasting station channel called satellite news gathering (SNG) and program broadcasting.

FIG. 1 is a block diagram showing the configuration of the main part of an embodiment of the present invention. In the figure, the center frequency of the baseband signal SBS (see FIGS. 5 and 6) output from the FM demodulation circuit (not shown) supplied to the input terminal 1 is 5.727272 MHz (PCM carrier frequency). QPSK demodulation circuit 3 via band pass filter 2
Is supplied to. In this case, the pass band of the band pass filter 2 is set so as to be wide so that the signal of the entire band of the PCM audio signal passes, and has a pass band of 1 MHz, for example.

The QPSK demodulation circuit 3 demodulates the QPSK-modulated PCM voice signal into an I / Q signal. This QP
The demodulation output signal output from the SK demodulation circuit 3 is supplied to the PCM decoder 4. As is well known, PCM decoder 4
Outputs a digital audio signal (not shown).

Further, the PCM decoder 4 detects whether or not the bit of C7 in the PCM audio data is "1". The PCM decoder 4 outputs the detection signal SD1 which becomes a low level "0" when the bit of C7 is "1" and becomes a high level "1" when the bit of C7 is "0". . This detection signal SD1 is supplied to one input terminal of the OR circuit 8.

The baseband signal SBS supplied to the input terminal 1 is also supplied to the detection circuit 6 via the bandpass filter 5 having a center frequency of 5.727272 MHz. In this case, the pass band of the band pass filter 5 is
It is set narrow so that the vicinity of the carrier of the PCM audio signal passes.

In the detection circuit 6, the signal extracted by the bandpass filter 5 is converted into a DC value, this DC signal is supplied to the voltage comparator 7 and compared with the reference level, and extracted by the bandpass filter 5. The level of the carrier thus selected is determined. The voltage comparator 7 outputs a detection signal SD2 of the carrier of the PCM audio signal, and the detection signal SD2 is supplied to the other input terminal of the OR circuit 8.

In this case, when the baseband signal SBS is of the first type and has a PCM audio signal, the level of the DC signal output from the detection circuit 6 becomes large, but at this time, the detection signal SD2 becomes The low level is set to "0". On the other hand, when the baseband signal SBS is of the second type and has an FM audio signal, the level of the DC signal output from the detection circuit 6 becomes small, but at this time, the detection signal SD2 has a high level "1". It becomes ".

The output signal of the OR circuit 8 is output to the output terminal 9
When the signal obtained at the output terminal 9 is at a high level "1", the muting control of video and audio is performed, although not shown.

As described above, in this example, when the C7 bit of the PCM voice data is "0" and the CS communication is performed, the detection signal SD1 becomes the high level "1", and therefore the output signal of the OR circuit 8 is Since it becomes the high level “1”, it is possible to mute the video and audio.

When the baseband signal SBS is of the second type and has an FM audio signal, the PC
The detection signal SD1 output from the M decoder 4 may become unstable and may be at a high level "1". However, in this case, since the level of the DC signal output from the detection circuit 6 becomes low, the detection signal SD2 becomes high level "1", and therefore the output signal of the OR circuit 8 becomes high level "1", and the video and audio are Muting can be done reliably.

Next, another embodiment of the present invention will be described. FIG. 2 is a block diagram showing the configuration of the embodiment. 2, parts corresponding to those in FIG. 1 are designated by the same reference numerals, and detailed description thereof will be omitted.

In the figure, the QPSK demodulation circuit 3 outputs a signal having a DC value corresponding to the lock state to the QPSK carrier, and this DC signal is supplied to the voltage comparator 7 to be compared with the reference level and QPSK. It is detected whether or not the carrier is locked. And the voltage comparator 7
Outputs a detection signal SD3 indicating a lock state to the QPSK carrier, and the detection signal SD3 is supplied to the other input terminal of the OR circuit 8.

In this case, when the baseband signal SBS is of the first type and has a PCM voice signal, the QPSK demodulation circuit 3 is locked to the QPSK carrier and is output from the QPSK demodulation circuit 6. The level of the DC value becomes larger, but at this time the detection signal S
D3 is set to the low level "0". On the other hand, when the baseband signal SBS is the second type and has the FM audio signal, the level of the DC value output from the QPSK demodulation circuit 6 becomes small, but at this time, the detection signal SD3 is at the high level " 1 ".

Here, FIG. 3 is a block diagram showing a specific configuration of the QPSK demodulation circuit 3. In the figure, input terminal 3
01 is supplied with a QPSK modulated signal SQP,
The K modulation signal SQP is supplied to the balanced modulators 302 and 303. The balance modulator 302 has a VCO (voltage controlled oscillator) 3
The carrier output from 04 is supplied as it is, and the carrier output from the VCO 304 is phase-shifted by 90 ° in the phase shifter 305 and supplied to the balanced modulator 303.

The output signals of the balanced modulators 302 and 303 are passed through the low-pass filters 306 and 307 to the limiter 30.
It is supplied to 8,309. Then, the limiters 308 and 3
The demodulation output signals (I / Q signals) of the in-phase axis and the quadrature axis are output from 09 and are output to output terminals 310 and 311 respectively.

The output signals of the limiters 308 and 309 are supplied to the balanced modulators 312 and 313, and the balanced modulators 312 and 313 have a low-pass filter 30.
The output signals of 7,306 are supplied. The output signals of the balanced modulators 312 and 313 are supplied to the adder 314, and the output signal of the adder 314 is supplied as a phase error signal to the control terminal of the VCO 304 via the low pass filter 315.

The demodulated output signal output from the limiter 309 is supplied to the bandpass filter 316 having a center frequency of 5.727272 MHz. In this case, if a QPSK modulated signal is supplied to the input terminal 301, for example, 2
A sine wave of 5.727272 MHz of about 00 mVp-p is obtained. Q extracted by the bandpass filter 316
The carrier of the PSK modulated signal is amplified by the amplifier 317 and then supplied to the detection circuit 318 and converted into a DC value.
Then, the detection circuit 318 outputs a signal having a DC value corresponding to the lock state to the QPSK carrier, and this is output to the output terminal 319.

Note that the output signal of the limiter 308 can be used instead of the output signal of the limiter 309 to obtain the signal of the DC value corresponding to the lock state to the QPSK carrier.

Returning to FIG. 2, the output signal of the OR circuit 8 is led to the output terminal 9, and although not shown, when the signal obtained at the output terminal 9 becomes a high level "1", the video and audio signals are muted. Control is performed.

The present example is constructed as described above, and the others are constructed in the same manner as the example of FIG.

In this example, as in the example of FIG.
When the C7 bit of the M voice data is “0” and the CS communication is performed, the detection signal SD1 becomes the high level “1”,
Therefore, the output signal of the OR circuit 8 becomes the high level "1", so that the video and audio can be muted.

If the baseband signal SBS is of the second type and has an FM audio signal, the
The detection signal SD1 output from the M decoder 4 may become unstable and may be at a high level "1". However, in this case, since the QPSK demodulation circuit 3 does not lock to the QPSK carrier, the detection signal SD3 becomes high level "1", and therefore the output signal of the OR circuit 8 becomes high level "1", so that the video and audio signals are output. Can be muted reliably.

The portion surrounded by a broken line in the example of FIG. 2 can be integrated and built in the QPSK demodulation circuit 3 or the PCM decoder 4.

Next, still another embodiment of the present invention will be described. FIG. 4 is a block diagram showing the configuration of the embodiment. 4, parts corresponding to those in FIG. 1 are designated by the same reference numerals, and detailed description thereof will be omitted.

In the same figure, as in the example of FIG. 1, the PCM decoder 4 detects whether or not the bit of C7 in the data area is "1", and the frame of the PCM data frame (see FIG. 7). Sync detection is performed. P
The CM decoder 4 outputs a detection signal SD4 which is at a low level "0" when frame synchronization is detected, and at a high level "1" when frame synchronization is not detected. This detection signal SD4 is supplied to the other input terminal of the OR circuit 8.

In this case, when the baseband signal SBS is of the first type and has a PCM audio signal, the PCM decoder 4 detects frame synchronization.
At this time, the detection signal SD4 is set to the low level "0". On the other hand, when the baseband signal SBS is of the second type and has an FM audio signal, frame synchronization is not detected by the PCM decoder 4, but at this time the detection signal SD4 becomes a high level "1". To be

The output signal of the OR circuit 8 is output to the output terminal 9
When the signal obtained at the output terminal 9 is at a high level "1", the muting control of video and audio is performed, although not shown.

The present example is constructed as described above, and the others are constructed in the same manner as the example of FIG.

In this example, as in the example of FIG.
When the C7 bit of the M voice data is “0” and the CS communication is performed, the detection signal SD1 becomes the high level “1”,
Therefore, the output signal of the OR circuit 8 becomes the high level "1", so that the video and audio can be muted.

When the baseband signal SBS is of the second type and has an FM audio signal, the
The detection signal SD1 output from the M decoder 4 may become unstable and may be at a high level "1". However, in this case, since the PCM decoder 4 does not detect frame synchronization in the PCM data frame, the detection signal SD4
Becomes a high level "1", and therefore the output signal of the OR circuit 8 becomes a high level "1", so that the video and audio can be reliably muted.

The portion surrounded by the broken line in the example of FIG. 4 can be integrated and built in the QPSK demodulation circuit 3 or the PCM decoder 4.

Further, in the above-mentioned embodiment, it is explained that both the video and the audio are muted, but only one of them can be muted.

[0049]

According to the present invention, the data included in the PCM audio data for determining whether or not the CS broadcast is detected,
Since the video and audio are muted based on the detected output, the video and audio can be mutated well during CS communication.

Further, the carrier of the PCM audio signal is detected, the lock state to the QPSK carrier is detected, or the frame synchronization in the PCM data frame is detected, and the video and audio are muted based on the detection output. Even when the television broadcast signal has an FM audio signal, the video and audio can be reliably muted.

[Brief description of drawings]

FIG. 1 is a block diagram showing a configuration of a main part of an embodiment of the present invention.

FIG. 2 is a block diagram showing a configuration of a main part of another embodiment of the present invention.

FIG. 3 is a block diagram showing a specific configuration example of a QPSK demodulation circuit.

FIG. 4 is a block diagram showing a configuration of a main part of another embodiment of the present invention.

FIG. 5 is a diagram showing frequency allocation of a television broadcast signal having a PCM audio signal.

FIG. 6 is a diagram showing frequency allocation of a television broadcast signal having an FM audio signal.

FIG. 7 is a diagram showing a structure of a PCM data frame.

[Explanation of symbols]

 1 Input Terminal 2, 5 Band Pass Filter 3 QPSK Demodulation Circuit 4 PCM Decoder 6 Detection Circuit 8 OR Circuit

Claims (4)

[Claims] 1. A detection means for detecting data included in PCM audio data for determining whether or not it is a CS broadcast, and muting at least one of video and audio based on a detection output of the detection means. A characteristic satellite broadcasting receiver. 2. A first detecting means for detecting data included in the PCM audio data for determining whether or not it is a CS broadcast,
Satellite broadcasting reception characterized by comprising a second detecting means for detecting a carrier of a PCM audio signal, and muting at least one of video and audio on the basis of detection outputs of the first and second detecting means. apparatus. 3. A first detecting means for detecting data included in the PCM audio data for determining whether or not it is a CS broadcast,
Satellite broadcasting comprising a second detecting means for detecting a lock state to the QPSK carrier, and muting at least one of video and audio based on the detection output of the first and second detecting means. Receiver. 4. A first detection means for detecting data included in the PCM audio data for determining whether or not it is a CS broadcast,
Second detection means for detecting a synchronization signal in the PCM audio data, and muting at least one of video and audio based on the detection output of the first and second detection means. Satellite broadcasting receiver.