JPS6221391A - Scramble device - Google Patents

Abstract

PURPOSE:To prevent the output signal of a sound modulator from being deteriorated in a transmission passage and a receiver by frequency-converting the output signal of the sound modulator within the period of a timing signal. CONSTITUTION:An image carrier wave (b) is modulated in an image modulator 1 by a video base band signal (a) and an output signal (c) of an image modulator is FM modulated by an image FM modulator 11 during a synchronizing signal period in which a gate signal generator 5 generates a gate signal, converted into a higher frequency or a lower frequency than the image carrier wave to output an output signal (j) of the image FM modulator. A sound carrier wave (f) is modulated in a sound modulator 3 by a sound base band signal (e), an output signal (c) of the sound modulator is FM modulated by a sound FM modulator 12 during a timing signal period in which the gate signal generator 5 generates the gate signal, converted into a higher frequency or a lower frequency than the sound carrier wave to output an output signal (k) of the sound FM modulator. The output signal (j) of the image FM modulator and the output signal (k) of the sound FM modulator are synthesizidby a sinthesizer 6 and outputted as a high frequency signal (m).

Description

DETAILED DESCRIPTION OF THE INVENTION [Field of Industrial Application] The present invention relates to a scrambling device in a pay broadcasting system that provides broadcasting to specific subscribers.

[Conventional technology]

FIG. 3 is a system diagram showing a conventional scrambling device.

In FIG. 3, 1 is a video modulator that modulates a video carrier wave with a video baseband signal a and outputs a video modulator output signal C, and 2 is a video AM modulator that amplitude modulates the video modulator output signal C. A video AM modulator that outputs an output signal d, 3 an audio modulator that modulates an audio carrier wave f with an audio baseband signal e and outputs an audio modulator output signal g, and 4 amplitude modulates the audio modulator output signal g. 5 is a gate signal generator that generates a gate signal for determining the modulation period of the video AM modulator 2 and the audio AM modulator 4; This is a synthesizer that synthesizes a video AM modulator output signal d and an audio AM modulator output signal ri and outputs a high frequency signal i.

FIG. 4(a) is a waveform diagram showing the video AM modulator output signal d, and FIG. 4(b) is a waveform diagram showing the audio AM modulator output signal d. In FIG. 4(al), 7 indicates the waveform of the video synchronization signal, 8 indicates the waveform of the normal video modulation signal, T1 indicates the synchronization signal period, and in FIG. 4(b), 9 indicates the waveform of the audio timing signal, 10 is the waveform of the normal audio modulation signal, T2
indicates the timing signal period.

Next, the operation of the conventional scrambling device will be explained using FIG. 3. Video carrier wave is video baseband signal a
According to the video modulator 1. As a result, the video modulator 1 outputs the video modulator output signal C. Next, the video modulator output signal C is A and M modulated by the video AM modulator 2 while the gate signal is being generated from the gate signal generator 5, so that the video AM modulator 2 outputs the video AM modulator output signal. Output d.

The audio carrier wave f is modulated by the audio modulator 3 by the audio baseband signal e, so that the audio modulator 3 outputs an audio modulator output signal g. Then the audio modulator output signal g
is AM-modulated by the audio AM modulator 4 while the gate signal is being generated from the gate signal generator 5, and thereby the audio AM modulator 4 outputs the audio AM modulator output signal.

The video AM modulator output signal d and the audio AM modulator output signal are combined by a synthesizer 6 and output as a high frequency signal i.

Note that the gate signal period applied to the audio AM modulator 4 is earlier in time than the gate signal period applied to the video AM modulator 2 -0 For example, the audio timing signal is 2 μs earlier than the video synchronization signal.

[Problem that the invention seeks to solve]

In the above-mentioned scrambling system, the demodulation start point of the video signal on the receiver side must be detected using the audio AM modulator output signal, but in the conventional scrambling system, the audio AM modulator output signal is detected. distortion,
There was a problem with deterioration.

The present invention has been made in view of these points, and its purpose is to provide a scrambling device that can prevent the audio AM modulator output signal from deteriorating in the transmission path and receiver. be.

[Means for solving problems]

To achieve this purpose, the present invention provides a video FM system that converts the frequency of the video modulator output signal within the synchronization signal period to a frequency higher or lower than the frequency of the video carrier wave.
a modulator and an audio F that converts the frequency of the audio modulator output signal within the timing signal period required to demodulate the video to a frequency higher or lower than the frequency of the audio carrier.
In this embodiment, an M modulator is provided.

[Effect]

In the present invention, by frequency-converting the audio modulator output signal within the timing signal period, it is possible to prevent deterioration of the modulated audio signal in the transmission path and receiver, and the video modulator output only during the synchronization signal period. By frequency converting the signal, there is no effect on the normal video modulation signal within the video period.

〔Example〕

FIG. 1 is a system diagram showing an embodiment of a scrambling device according to the present invention. In FIG. 1, 1 is a video modulator that modulates a video carrier wave with a video baseband signal a and outputs a video modulator output signal C, and 11 is a video FM modulator that frequency-modulates the video modulator output signal C. a video FM modulator that outputs an output signal j; 3 a modulator that modulates an audio carrier wave f with an audio baseband signal e and outputs an audio modulator output signal g; 12 a modulator that frequency-modulates the audio modulator output signal g; an audio FM modulator that outputs an audio FM modulator output signal k;
6 is a gate signal generator that generates a gate signal for determining the modulation period of the video FM modulator 2 and the audio FM modulator 4, and 6 is a gate signal generator that synthesizes the video FM modulator output signal j and the audio FM modulator output signal. This is a synthesizer that outputs a high frequency signal m.

Fig. 2 (al indicates the waveform of the video FM modulator output signal j, and Fig. 2 (b) shows the waveform of the audio FM modulator output signal. In Fig. 2 (a), 13 indicates the video synchronization signal 8 is the waveform of a normal video modulation signal, T1 is a synchronization signal period, and in FIG. 2 ('b), 14 is a waveform of an audio timing signal, 10 is a waveform of a normal audio modulation signal, T2
indicates the timing signal period.

Next, the operation of this device will be explained using FIG. The video carrier wave is modulated by the video baseband signal a in the video modulator 1, so that the video modulator 1 outputs a video modulator output signal C. Next, the video modulator output signal C is FM-modulated by the video FM modulator 11 during the synchronization signal period in which the gate signal generator 5 is generating the gate signal, and is converted to a frequency higher or lower than that of the video carrier wave.

Thereby, the video FM modulator 11 outputs the video FM modulator output signal j.

The audio carrier wave f is modulated by the audio baseband signal e in the audio modulator 3, so that the audio modulator 3 outputs an audio modulator output signal C. Then the audio modulator output signal C
is FM-modulated by the audio FM modulator 12 during the timing signal period when the gate signal generator 5 is generating the gate signal, and is converted to a frequency higher or lower than the audio carrier wave.

Thereby, the audio FM modulator 12 outputs the audio FM modulator output signal k.

The video FM modulator output signal j and the audio FM modulator output signal are combined by a synthesizer 6 and output as a high frequency signal m.

In the above embodiment, as shown in FIG.
For example, the gate signal period, that is, the timing signal period that is applied to the audio FM modulator 12 is 2.
Occurs μs earlier.

In the above embodiment, one gate signal waver that determines the frequency conversion (FM modulation) period converts the frequency of the video modulator output signal C and the audio modulator output signal.
A gate signal generator that determines the timing signal period of the audio FM modulator output signal may be provided separately from the gate signal generator that determines the synchronization signal period of the modulator output signal j. Also,
The video gate signal generated by the gate signal generator may be used only for the horizontal synchronization period, only for the vertical synchronization period, or for both the horizontal and vertical synchronization periods, and the same applies to the audio carrier wave. Alternatively, only the video carrier wave may be frequency converted.

〔Effect of the invention〕

As explained above, the present invention provides a video FM modulator that converts the frequency of a video modulator output signal within a synchronization signal period to a frequency higher or lower than the frequency of a video carrier wave, and a timing necessary for demodulating video. By providing an audio FM modulator that converts the frequency of the audio modulator output signal within the signal period to a frequency higher or lower than the frequency of the audio carrier wave, the influence of scrambling on the normal video modulation signal within the video period is eliminated. This has the effect of preventing deterioration of the audio modulation signal in the transmission path and receiver.

[Brief explanation of the drawing]

FIG. 1 is a system diagram showing an embodiment of a scrambling device according to the present invention, FIG. 2 is a waveform diagram for explaining its operation, FIG. 3 is a system diagram showing a conventional scrambling device, and FIG.
The figure is a waveform diagram for explaining the operation. 1...Video modulator, 3...Audio modulator, 5...
...Gate signal generator, 6...Synthesizer, 11...
-Video FM modulator, 12...Audio FM modulator. Figure 1 Suden Figure 2 Figure 3 Figure 4 Procedural amendment (voluntary) Showa 6Q (211F120th)

Claims (1)

[Claims] In a scrambling device in a pay broadcasting system that provides broadcasting to a specific subscriber, a video FM modulator converts the frequency of a video modulator output signal within a synchronization signal period to a frequency higher or lower than the frequency of a video carrier wave; an audio FM modulator that converts the frequency of the audio modulator output signal within a timing signal period necessary for demodulating the audio frequency to a frequency higher or lower than the frequency of the audio carrier wave.