JPH02101834A - Scrambler, encoder and decoder for the same scrambler - Google Patents

Abstract

PURPOSE:To attain a scramble processing for a TV broadcasting signal by mixing a modulation signal modulating a carrier with a video base band signal and an audio base band signal with a local oscillation signal generated by specifying the modulation signal. CONSTITUTION:An intermediate frequency modulation section 2 uses a base band video signal inputted from a video signal input terminal 2a to apply AM modulation to a video carrier in a prescribed frequency and uses an audio signal inputted from a base band audio input terminal 2b to apply FM modulation to an audio carrier. The generated intermediate frequency modulation signal fIPM is added and mixed with a local oscillation signal supplied from a local oscillation section 6 at a mixer section 4. The local oscillation section 6 uses an FM modulation section 8 to apply FM modulation with a signal from a signal source 10, thereby generating a local oscillation signal frequency- shifted from a reference frequency over a wider range than a pull-in enable frequency range of a conventional automatic frequency control circuit. Thus, a TV broadcast signal is scrambled.

Description

DETAILED DESCRIPTION OF THE INVENTION <Industrial Application Field> The present invention relates to a scrambling device that allows only specific viewers to receive television broadcasts, and an encoder and decoder for this device.

<Prior Art> Conventionally, encoders for the above-mentioned Sfuranzl apparatus have been ones that individually scramble a baseband video signal and a baseband audio signal, respectively.
Some devices scramble only the baseband video signal. Methods of scrambling baseband video signals include methods that transform the synchronization signal part of the video signal, methods that convert the polarity of the baseband video signal, and methods that superimpose interference waves on the baseband video signal. , the scanning lines of the baseband video signal are replaced, or the scanning lines are replaced midway.

<Problems to be Solved by the Invention> However, since each of the above methods involves scrambling the baseband signal, an encoder is provided in the portion of the television signal modulator that handles the baseband video signal. .

Therefore, the circuit configuration becomes complicated and the cost of the television signal modulator becomes high. Furthermore, since the baseband signal is scrambled, when the scrambling is canceled (descrambled) on the decoder side to obtain the baseband video signal, an image of good quality cannot be obtained.

Furthermore, each of the above methods requires an encoder for each baseband video signal, making the configuration even more complex.

Furthermore, if each audio signal is also scrambled, an encoder must be provided for each audio signal, making the configuration even more complex. Furthermore, a control signal for descrambling must be added to the scrambled signal and transmitted to each decoder, which increases the complexity of the circuit configuration. Furthermore, in order to descramble the encoder with such a complicated configuration, the encoder becomes correspondingly complicated and the cost increases.

An object of the present invention is to provide a scrambling device that solves the above-mentioned problems, and an encoder and decoder for the same.

Means for Solving the Problems> The encoder of the first invention includes a local oscillation section and a mixing section. The local oscillation section generates a local oscillation signal whose frequency is shifted from a reference frequency over a wider range than the frequency range that can be pulled in by a normal automatic frequency control circuit. A modulated signal obtained by modulating a carrier wave with a video baseband signal and an audio baseband signal is input to the mixing section, and this is mixed with the frequency-shifted local oscillation signal to generate a scrambled broadcast signal. .

In the encoder of the second aspect of the invention, a plurality of modulation signals are supplied to the mixing section.

In the encoder of the third invention, not only a plurality of modulation signals are supplied to the mixing section, but also a pilot signal is supplied to the mixing section.

The decoder of the fourth invention descrambles a selected one of the plurality of scrambled broadcast signals supplied from the plurality of encoders of the first invention, and includes a local oscillation section, a selection section, and a mixing section. , and a control signal generator. The local oscillation section generates a second local oscillation signal whose frequency is shifted according to the supplied control signal. The selection section selects a specific one to be received from among the scrambled broadcast signals. The mixing section mixes the selected specific scrambled broadcast signal and the second local oscillation signal. The control signal generating section generates the control signal according to the frequency shift between the output signal of the mixing section and the carrier wave corresponding to this output signal.

The decoder of the fifth invention simultaneously descrambles each of a plurality of scrambled broadcast signals supplied from the encoder of the second invention, and, like the fourth decoder, includes a local oscillation section and a mixing section. , a selection section, and a control signal generation section. However, instead of selecting one of the scrambled signals and supplying it to the mixing section, the selection section selects a specific one from among a large number of scrambled signals whose frequency has been changed in the mixing section and controls the signal. It is supplied to the signal generation section. Further, the local oscillator has a frequency that deviates from the reference frequency according to the control signal.

The decoder of the sixth invention descrambles each scrambled broadcast signal from the encoder of the third invention, and in the fifth invention, the selection section selects a specific frequency-converted scramble signal from the output of the mixing section. The difference is that a frequency-converted pilot signal is selected.

A scrambling device according to a seventh invention includes a combination of a plurality of encoders according to the first invention and a decoder according to the fourth invention.

A scrambling device according to an eighth invention includes the encoder according to the second invention and the decoder according to the fifth invention.

A scrambling device according to a ninth invention includes the encoder according to the third invention and the decoder according to the sixth invention.

Effect> In the encoder of the first invention, in the mixing section, the modulation signal modulated by the audio signal and the video signal is mixed with the local oscillation signal of the local oscillation section and frequency converted. has a frequency shift, so the frequency-converted signal also has a frequency shift. Moreover, this frequency deviation exceeds the frequency range that can be acquired by the automatic frequency control circuit (AFC) used in ordinary television receivers, etc., so the output signal of this mixing section is Even if the signal is supplied to a television receiver as is, good images and sound cannot be obtained; in other words, the signal is scrambled.

In the encoder of the second invention, since a plurality of modulation signals are supplied to the mixing section, it is possible to scramble a plurality of modulation signals at the same time.

In the third invention, the plurality of modulated signals are scrambled, and the pilot signal is also scrambled and sent out. This pilot signal
It is used when descrambling with the decoder of the invention.

In the decoder of the fourth aspect of the invention, one of the plurality of scrambled and frequency-converted modulation signals selected by the selection section is supplied to the mixing section. This is mixed with the local oscillation signal of the local oscillator in the mixer and frequency-converted.

Although this frequency-converted signal has a one-frequency shift, the control signal generating section generates a control signal corresponding to the frequency shift and supplies it to the local oscillation section. As a result, the frequency of the local oscillation signal of the local oscillation section follows the deviation, and this is supplied to the mixing section. Therefore, the output signal of the mixer has one frequency deviation removed. In other words, the scramble is canceled.

In the decoder of the fourth invention, the selected one modulation signal is descrambled, but in the decoder of the fifth invention, each frequency-converted and frequency-shifted signal is combined with the local oscillation signal in the mixing section. and are frequency-converted to modulated signals of the respective original frequencies. In this case, the fourth
As with the invention, the frequency shift remains. A selection section selects a specific one of these, and a control signal generation section generates a control signal corresponding to the frequency deviation of the selected signal, which is then supplied to the local oscillation section, so that the frequency of the local oscillation signal becomes equal to the frequency. Follow deviations. Therefore, the frequency deviation of each signal output from the mixing section is removed, and each signal is descrambled.

In the decoder of the sixth aspect of the invention, the selection section selects the pilot signal that has been frequency-converted to the original frequency and has a frequency shift, instead of the modulation signal that has been frequency-converted and has a frequency shift from the mixing section. Or, it is different from the fifth invention.

The scrambling devices of the seventh to ninth inventions are a combination of the encoders of the first to third inventions described above and the decoders of the fourth to sixth inventions, so from the above description, it is clear that these scrambling devices Since the effect is obvious, detailed explanation will be omitted.

<Example> A first example is shown in FIGS. 1 to 3. In this embodiment, the present invention is implemented in a scrambling device for a communal viewing and viewing device. FIG. 1 is a block diagram of an encoder of the scrambling device, which is provided, for example, in an independent broadcast section of a head end of a communal viewing device. Reference numeral 2 denotes an intermediate frequency modulation section which performs AM modulation on a video carrier wave of a predetermined frequency using a baseband video signal inputted from a video signal input terminal 2a, and modulates an audio carrier wave with an audio signal inputted from a baseband audio input terminal 2b. FM modulate. The modulation signal modulated by the video signal and the modulation signal modulated by the audio signal are hereinafter collectively referred to as an intermediate frequency modulation signal txra.

This intermediate frequency modulated signal f□ is added and mixed in the mixer 4 with a local oscillation signal supplied from one local oscillator 6, and frequency-converted into a scrambled television broadcast signal.

The local oscillator 6 has an FM modulator 8, which converts the intermediate frequency modulation signal f1□ into a television broadcast signal rrv having a frequency receivable by a commercially available television receiver. A carrier wave fL having the necessary local oscillation frequency for conversion.

FM with a signal from a signal source 10 having an appropriate frequency.
It modulates. Since FM modulation is performed in this way, the local oscillation signal supplied from the FM modulator 8 to the mixer 4 has a fi frequency deviation within the range of ±Δf with fLo as a reference. Automatic frequency control circuit (A) used in television receivers etc.
The frequency and level of the signal source 10 are selected so that the frequency range is larger than the usable frequency range. Note that as the signal source 10, for example, a commercial AC power source can be used. In this case, the frequency deviation range ±Δf is
Set by adjusting the level of commercial AC power. Note that instead of such local oscillation section 6, a sweep oscillation section that sweeps a certain frequency range within a certain time may be used.

FIG. 2 shows the intermediate frequency modulation signal ffFMi local oscillation signal f
This shows the relationship between Lo±Δf and the television broadcast signal fTV±Δf. As is clear from this, the scrambled television broadcast signal fTV±Δf has the intermediate frequency modulation signal f, f shifted in frequency. Local oscillation signal fL
Since the frequency is converted by o±Δf, the frequency is shifted within the range of ±Δf.

In this way, the scrambled television broadcast signal, which is the output signal of the mixing section 4, has a frequency shift of fTV±Δf, and the range of this frequency shift is limited to the AFC of commercially available television receivers. Since the signal exceeds the retractable range, even if the scrambled television broadcast signal fTV±Δf is received by a commercially available television receiver, both the video and audio are distorted and cannot be received well. . In other words, the data is scrambled. Note that the encoder shown in FIG. 1 can only scramble one baseband television signal consisting of one video baseband signal and one audio baseband signal, so it can scramble multiple baseband television signals. If the signal is to be scrambled, a plurality of sets of encoders shown in FIG. 1 may be prepared; of course, in that case, the oscillation frequency fLo of the local oscillation signal must be different for each encoder.

FIG. 3 is a block diagram of a receiver equipped with an encoder for descrambling the scramble applied as described above.
4 and an intermediate frequency demodulator 16. This receiver is provided, for example, for each terminal of the communal viewing and viewing device.

The descramble tuner 12 corresponds to a decoder, and its high frequency input terminal 18 is supplied with scrambled television broadcast signals from a plurality of encoders having the configuration shown in FIG. 1, respectively. The reference frequency fTV of these scrambled television broadcast signals differs for each encoder. The tuner section 20 selects one specific scrambled television broadcast signal from among these television broadcast signals according to the signal from the channel selection section 13 and supplies it to the mixing section 22 . That is, the tuner section 20 functions as a selection section.

The mixing section 22 is also supplied with a local oscillation signal from the variable oscillation section 24 . The variable oscillator 24 generates a local oscillation signal necessary to convert the selected scrambled television broadcast signal fTV±Δf into a predetermined intermediate frequency signal rrr.
It oscillates in response to a signal from the tuning section 13. Therefore, ~ the selected scrambled television broadcast signal is frequency-converted to an intermediate frequency signal, but since the originally selected television broadcast signal has a frequency deviation of ±Δf, the frequency-converted intermediate frequency signal ffF also has a frequency deviation of ±Δf.

This signal is amplified by the intermediate frequency amplification section 14 and supplied to a wideband automatic frequency control circuit (AFC) 26. This broadband A
The FC 26 has a wider pull-in range than a normal AFC, and can generate a control signal corresponding to a frequency deviation of ±Δf. This control signal is supplied to the variable oscillation section 24. As a result, the oscillation frequency of the variable oscillator 24 is adjusted according to the frequency deviation ±Δf of the television broadcast signal.
The frequency shift, that is, the scrambling, of the intermediate frequency signal flF, which has a frequency shift of Δf and is output from the mixing section 22, is canceled.

This unscrambled intermediate frequency signal r□ is amplified by the intermediate frequency amplification section 14, demodulated into a baseband video signal and a baseband audio signal by the intermediate frequency demodulation section 16, and then sent to the baseband video signal output terminal 28, the baseband The audio signal is supplied from the audio signal output terminal 30 to a baseband video signal input terminal and a baseband audio signal input terminal of a television receiver (not shown), respectively. Note that it is also possible to provide only the descrambling tuner 12 and connect its output signal to the antenna terminal of the television receiver. specific television broadcast signals,
The configuration may be such that a local oscillation signal having a frequency that can be frequency-converted to any one of a plurality of channels receivable by the television receiver is generated in response to a signal from the channel selection section 13.

Further, in this case, a signal may be supplied to the wideband AFCZ 6 from an intermediate frequency amplifying section in the television receiver or from the output side of the mixing section 22. Furthermore, by adding data to the signal from the encoder signal source 10, specific additional information can be sent only to terminals that have the descramble tuner 12.

A second embodiment is shown in FIGS. 4 and 5. In this embodiment, the present invention is also implemented in a scramble device for a communal viewing and viewing device. In this embodiment, the encoder is then installed in a converter integrated into the headend. Note that the converter is used to receive television broadcast signals transmitted from each broadcast station with an antenna, and retransmit them at frequencies different from each reception frequency.

FIG. 4 is a block diagram of the converter, which has an RF input section 32. This RF input section 32 has an antenna (
(not shown) is the television broadcast signal fT from each broadcast station.
It receives each of V1 to fTVn and makes their amplitude levels the same. Each of the television broadcast signals fTVl to fTVn from the RF input unit 32 has relatively close frequencies, and is sent to the mixing unit 34.
supplied to

The mixing unit 34 is supplied with a frequency-shifted local oscillation signal rLo±Δf from the local oscillation unit 6a. This local oscillator 6a is composed of an FM modulator 8a and a signal source 10a as in the first embodiment, and FM-modulates a carrier wave having a frequency fLo with a signal from the signal [10a, and has a frequency deviation of ±Δf. It was moved. Of course, this frequency shift range is outside the range that can be captured by the AFC of commercially available television receivers and the like.

Each of the television broadcast signals fTν to fTVn is frequency-converted by the frequency-shifted local oscillation signal fLo±Δf to become frequency-converted scrambled television broadcast signals fcI±Δf to fen±Δf. That is, in this embodiment, multiple television broadcast signals are simultaneously scrambled. These scrambled television broadcast signals are amplified by the RF output section 36 and supplied to the main line of the communal viewing device. As shown by the dotted line, a pilot signal generator 38 is provided, and this pilot signal is supplied to the mixing section 34, which is also frequency-converted using the frequency-shifted oscillation signal from the oscillation section 6a, and is sent to the main line. This is used when descrambling is performed by a decoder, which will be described later.

Figure 5 shows each station wave number conversion scrambled television broadcast signal ret±Δ which has been scrambled as described above.
FIG. 4 is a block diagram of a decoder 40 for simultaneously descrambling all of f to fCn±Δf. This decoder 40 is connected to a main line or a branch line 42 as shown in FIG.
Each scrambled station wave number converted scrambled television signal fcI±Δf to fCn± supplied from
.DELTA.f is descrambled and supplied to a plurality of television receivers 44, 44, . . . .

As shown in FIG. 5, this decoder 40 has an RF input section 46. As shown in FIG. The RF input section 46 amplifies each scrambled frequency-converted scrambled television broadcast signal fcI±Δf to ran±Δf supplied from the main line or branch line 42 and the frequency-converted scrambled pilot signal, and sends the scrambled frequency-converted scrambled pilot signal to the mixer 48. supply The mixing section 48 is also supplied with a local oscillation signal from the variable oscillation section 50. This variable oscillation section 50 has an F as shown in FIG.
It oscillates using the same frequency fLo as the carrier wave of the M modulator 8a as a reference frequency, and the oscillation frequency is changed according to a control signal from an automatic phase comparator (APC) 52, which will be described later. When the oscillation frequency of the variable oscillation unit 50 is the reference frequency, the frequency converted scrambled television broadcast signals fcI±Δf to fCn±Δf of each station and the frequency converted scrambled pilot signal converted to their original frequencies are converted to the mixing unit 48. Sent from However, they each have a frequency deviation of ±Δf. These are supplied from the RF output section 54 to a band pass filter 56. This bandpass filter 56 is configured to pass only the pilot signal whose pass band is shifted in frequency. That is, this bandpass filter 56 functions as a selection section. Bandpass filter 5
The frequency-shifted pilot signal selected in step 6 is
is supplied to the automatic phase comparison section 52, and this automatic phase comparison section 5
2 supplies the variable oscillation unit 50 with a control signal corresponding to the frequency shift between the original pilot signal and the frequency-shifted pilot signal. As a result, the oscillation frequency of the variable oscillator 50 becomes one corresponding to the frequency shift, and the frequency shift of each television broadcast signal and pilot signal is removed, and each of the television broadcast signals and pilot signals shown in FIG. It is supplied to television receivers 44, 44, . . . . Note that when the pilot signal generator 38 is not provided in the encoder shown in FIG.
The passband is set so that one of the frequency-shifted television broadcast signals output from the mixer 48 can be selected.

<Effects of the Invention> As described above, according to the encoder of the first invention, both an audio signal and a video signal (television broadcast signal) can be scrambled with a simple configuration of a mixing section and a local oscillation section. Can be done. According to the encoder of the second invention,
After all, multiple television broadcast signals can be scrambled with a simple configuration of a mixer and a local oscillator.

In the third invention, in addition to each television broadcast signal, the pilot signal is also supplied to the mixing section, so when descrambling a plurality of television broadcast signals at the same time,
Easy to do.

The decoder of the fourth invention includes a mixing section, a local oscillation section,
Scramble can be canceled with a simple configuration consisting of a control signal generator. In the fifth and sixth inventions, the oscillation frequency of the local oscillator is controlled by using the frequency-shifted pilot signal or the frequency-shifted television broadcast signal selected by the selection unit. , multiple television signals can be descrambled simultaneously.

A scrambling device according to a seventh invention is a combination of a plurality of encoders according to the first invention and a decoder according to the fourth invention, and has a simple configuration that scrambles a plurality of television signals and selects one of them. It is possible to unscramble the data with a simple configuration. The scrambling device of the eighth invention is a combination of the encoder of the second invention and the decoder of the fifth invention, and the scrambling device of the ninth invention is a combination of the encoder of the third invention and the decoder of the fifth invention. decoders, each with a simple configuration can simultaneously scramble multiple television signals, and can simultaneously descramble multiple scrambled television signals with a simple configuration. be able to.

[Brief explanation of the drawing]

FIG. 1 is a block diagram of a first embodiment of an encoder for a scrambling device according to the present invention, and FIG. 2 is a diagram showing the frequency relationship between the input signal and output signal of the mixing section of the encoder, and the local oscillation signal of the local oscillation section. . FIG. 3 is a block diagram of a first embodiment of a decoder for a scrambler according to the present invention, FIG. 4 is a block diagram of a second embodiment of an encoder for a scrambler according to the present invention, and FIG. 5 is a block diagram of a first embodiment of a decoder for a scrambler according to the present invention. FIG. 6 is a block diagram of a second embodiment of the device decoder. FIG. 6 is a block diagram showing how the decoder of FIG. 5 is used. 2...Intermediate frequency modulation section, 4.22.34.48...
...Mixing section, 6.6a...Local oscillation section, 20...
... Tuner section (selection section), 24.50... Variable oscillation section, 26... Wideband AFC (control signal generation section),
52... automatic phase comparison section (control signal generation section), 56
... Pantobus Builta (selection section). Patent applicant: DAYX Antenna Co., Ltd. Representative: Tetsu Shimizu and 2 other people

Claims (1)

[Claims] (1) A local oscillation unit that generates a local oscillation signal whose frequency is shifted from a reference frequency over a range wider than the frequency range that can be pulled in by a normal automatic frequency control circuit, and a video baseband signal and An encoder for a scrambling device, comprising a mixing section that generates a scrambled broadcast signal by mixing a modulation signal obtained by modulating a carrier wave with an audio baseband signal and the local oscillation signal. (2) The encoder for a scrambling device according to claim (1), wherein a plurality of the modulation signals are supplied to the mixing section. (3) The encoder for a scrambling device according to claim (2), wherein a pilot signal is also supplied to the mixing section. (4) A plurality of modulated signals in which a carrier wave is modulated with a video baseband signal and an audio baseband signal, respectively, and a frequency deviation from the reference frequency over a wider range than the frequency range that can be drawn by a normal automatic frequency control circuit. A decoder that descrambles a selected one of a plurality of scrambled broadcast signals mixed with a first local oscillation signal, and generates a second local oscillation signal whose frequency is shifted according to a supplied control signal. a local oscillation section; a selection section that selects a specific one of the scrambled broadcast signals; a mixing section that mixes the selected specific scrambled broadcast signal and a second local oscillation signal; A decoder for a scrambling device, comprising a control signal generating section that generates a control signal that generates the control signal according to a frequency deviation between an output signal and a normal frequency corresponding to the output signal. (5) A plurality of modulated signals in which a carrier wave is modulated with a video baseband signal and an audio baseband signal, respectively, and a frequency deviation from a reference frequency over a wider range than the frequency range that can be drawn by a normal automatic frequency control circuit. A decoder that receives a plurality of scrambled broadcast signals mixed with a first local oscillation signal, and generates a second local oscillation signal whose frequency is shifted from the reference frequency according to a supplied control signal. a mixing section that mixes each scrambled broadcast signal and a second local oscillation signal; a selection section that selects one of the output signals of the mixing section that corresponds to a specific scrambled broadcast signal; A decoder for a scrambling device, comprising: a control signal generating section that generates a control signal that generates the control signal according to a frequency shift between the output signal of the mixing section and the corresponding carrier wave. (6) Multiple modulation signals whose carrier waves are modulated with video baseband signals and audio baseband signals, pilot signal modulation signals whose carrier waves are modulated with pilot signals, and a frequency range that is wider than the frequency range that can be pulled in by a normal automatic frequency control circuit. A decoder for receiving a plurality of scrambled signals each mixed with a first local oscillation signal having a frequency deviation from a reference frequency over a range, the scrambled signal having a first local oscillation signal having a frequency deviation from the reference frequency in response to a supplied control signal. a local oscillation unit that generates a second local oscillation signal; a mixing unit that mixes each scrambled signal and the second local oscillation signal;
a selection section that selects one of the output signals of the mixing section that corresponds to the pilot signal; and a selection section that selects the one that corresponds to the pilot signal from among the output signals of the mixing section; A decoder for a scrambling device, comprising: a control signal generating section that generates a control signal that generates a control signal. (7) A plurality of encoders according to claim 1, and claim 4.
A scrambling device comprising the decoder described above. (8) A scrambling device comprising the encoder according to claim 2 and the decoder according to claim 5. (9) A scrambling device comprising the encoder according to claim 3 and the decoder according to claim 6.