CA1270941A - Video noise jammer - Google Patents
Video noise jammerInfo
- Publication number
- CA1270941A CA1270941A CA000550019A CA550019A CA1270941A CA 1270941 A CA1270941 A CA 1270941A CA 000550019 A CA000550019 A CA 000550019A CA 550019 A CA550019 A CA 550019A CA 1270941 A CA1270941 A CA 1270941A
- Authority
- CA
- Canada
- Prior art keywords
- signal
- multichannel
- noise
- channel
- obscured
- Prior art date
- Legal status (The legal status is an assumption and is not a legal conclusion. Google has not performed a legal analysis and makes no representation as to the accuracy of the status listed.)
- Expired - Lifetime
Links
Classifications
-
- H—ELECTRICITY
- H04—ELECTRIC COMMUNICATION TECHNIQUE
- H04K—SECRET COMMUNICATION; JAMMING OF COMMUNICATION
- H04K3/00—Jamming of communication; Counter-measures
- H04K3/80—Jamming or countermeasure characterized by its function
- H04K3/82—Jamming or countermeasure characterized by its function related to preventing surveillance, interception or detection
- H04K3/825—Jamming or countermeasure characterized by its function related to preventing surveillance, interception or detection by jamming
-
- H—ELECTRICITY
- H04—ELECTRIC COMMUNICATION TECHNIQUE
- H04K—SECRET COMMUNICATION; JAMMING OF COMMUNICATION
- H04K1/00—Secret communication
- H04K1/02—Secret communication by adding a second signal to make the desired signal unintelligible
-
- H—ELECTRICITY
- H04—ELECTRIC COMMUNICATION TECHNIQUE
- H04K—SECRET COMMUNICATION; JAMMING OF COMMUNICATION
- H04K3/00—Jamming of communication; Counter-measures
- H04K3/40—Jamming having variable characteristics
- H04K3/42—Jamming having variable characteristics characterized by the control of the jamming frequency or wavelength
-
- H—ELECTRICITY
- H04—ELECTRIC COMMUNICATION TECHNIQUE
- H04N—PICTORIAL COMMUNICATION, e.g. TELEVISION
- H04N7/00—Television systems
- H04N7/16—Analogue secrecy systems; Analogue subscription systems
- H04N7/166—Passage/non-passage of the television signal, e.g. jamming, band suppression
-
- H—ELECTRICITY
- H04—ELECTRIC COMMUNICATION TECHNIQUE
- H04K—SECRET COMMUNICATION; JAMMING OF COMMUNICATION
- H04K2203/00—Jamming of communication; Countermeasures
- H04K2203/10—Jamming or countermeasure used for a particular application
- H04K2203/14—Jamming or countermeasure used for a particular application for the transfer of light or images, e.g. for video-surveillance, for television or from a computer screen
Abstract
A B S T R A C T
A multichannel signal distribution control system, such as a CATV system, providing a plurality of video signal channels wherein selected channels are obscured by random noise jammer signals. The signal distribution system includes multiple output ports, each port connected to a respective user or subscriber. The random noise jammer signal is provided by a band-limited noise source and a signal translator which provides a noise signal band corresponding to the frequency of the channel to be selectively disabled. The resulting noise signal is added to the signals for specific individual subscriber output ports to obscure the signal on the selected channel of that individual subscriber. The multichannel signal distribution control system is controlled by signals provided remotely from a home office to each local jamming device by control signals superimposed on the multiple channel signal feed line.
A multichannel signal distribution control system, such as a CATV system, providing a plurality of video signal channels wherein selected channels are obscured by random noise jammer signals. The signal distribution system includes multiple output ports, each port connected to a respective user or subscriber. The random noise jammer signal is provided by a band-limited noise source and a signal translator which provides a noise signal band corresponding to the frequency of the channel to be selectively disabled. The resulting noise signal is added to the signals for specific individual subscriber output ports to obscure the signal on the selected channel of that individual subscriber. The multichannel signal distribution control system is controlled by signals provided remotely from a home office to each local jamming device by control signals superimposed on the multiple channel signal feed line.
Description
~7l3~
FIELD OF THE INVENTIONi 1 The present invention relates to secure video signal
FIELD OF THE INVENTIONi 1 The present invention relates to secure video signal
2 distribution systems and, in particular, to multichannel signal
3 distribution control systems providing random noise jamming of
4 selected information channels.
BACKGROUND OF THE INVEN~ION
Broadband, multichannel signal distribution systems 6 orovide secure channel signal allocation to selected 7 subscribers. In the past, security of the channel information has been provided by two methods, either passive trapping or ~ removal of the channel information, or signal jamming or obscuring the channel information with a secondary signal to 11 make the channel information unusable. In passive trapping, an 1~ electronic band-stop filter is installed in the customer's 13 connection (drop) to eliminate those signals which the customer 14 is not authorized to receive. The passive trap is typically installed at the drop, and may be actuated at the drop either 1~ manually or electronically by a control signal from a remote : .., ~. ., . ;
: .: .. . . . .
~, ~.".,.,i , :. , L~L
1 control point. ~owever, signal traps are subject to frequency 2 drift under changing temperature, and the temperature drift 3 causes the signal trap to drift from the carrier frequency, 4 ~hus allowing unauthorized customer access to the channel.
Moreover, as signal traps tend to be quite wide in bandwidth at 6 higher frequencies, the use of such filters is made 7 economically unfeasi~le or, alternately, makes the adjacent ~ channels also unusable.
9 Signal jamming typically provides a narrow band continuous wave (CW) carrier or modulated carrier which is added to the 11 signal channel of interest. To recover the signal, the 1~ authorized customer is given a narrow band trap to remove the 13 jamming signal. However, the trap used to remove the jamming 14 is also subject to temperature drift. When the drift occurs, a recovered signal could hecome unusable or marginally usable.
16 ~toreover, the trap may remove not only the jamming carrier but 1~ also some of the desired signal, thus degrading the quality of 18 the received signal. Furthermore, since a trap of this nature 19 is installed at the customer location, a customer having electronic knowledge can easily design a device to remove the ~1 jamming signal and thus recover the desired signal without authorization.
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SUMMARY OF THE INVENTION
1 The multichannel signal distribution control system 2 according to the present invention completely obscures the 3 selected channel or channels by providing a band-limited noise 4 signal to mask the selected channel signal. Signal parameters S are easily maintained such that the jamming noise signal is limited only to the desired channel or channels, and problems 7 arising due to temperature drift or instability are avoided.
3 ~loreover, the obscured signal is unrecoverable by customer g apparatus since the obscuring signal contains no coded key and is not limited to a narrow frequency band.
11 The apparatus according to the present invention comprises 1~ a baseband noise generator having a noise signal band-limiting 13 ~ilter. T,he resulting band-limited noise source is translated 14 to the channel of interest by a signal translator. Each drop includes at least one signal translator for each secured 1~ channal or group of channels to be controlled. The frequency 1~ translator comprises a local oscillator of a frequency 18 corresponding to the center of the desired channel or group of ~7~3~
1 channels. The local oscillator signal and the baseband signal 2 are received by a balanced mixer to provide the noise source at 3 the selected channel(s) frequency and to suppress the other 4 ~ixer signal components in the mixer output signal. The S -esulting translated.noi.se signal..and a portion of the incoming 6 wideband multichannel signal are combined to provide the user 7 with all signal channels provided by the multichannel ~ distribution system, plus the selected frequency noise jamming 9 signal at the specified channel(s) to be selectively obscured.
The translated noise sources are remotely controlled by a 11 coded signal provided along the multïchannel signal feed from 1~ the home office as received and decoded by a signal decoder and 13 jammer control processor unit.
DESCRIPTION OF THE DRAWING
1~ These are other features according to the present ~nvention will be further understood by reading the following 1~ ~etailed description of the invention, taken together with the 7 drawing wherein:
18 Fig. 1 is a block diagram of one embodiment of the present 9 invention; and , ~, , ~ " . , , , ,, , ~
~'~ 7 ~
1 Fig. 2 is a block diagram of a second embodiment according to the present invention.
DETAILED DESCRIPTION OF THE INVENTION
3 The block diagram of one embodiment of the present 4 invention is shown in Fig. l, wherein the multiple channels of Yideo signals are received from the home office (not shown) 6 along a signal path 52, rom which a plurality of slgnals 54 7 are provided by a si~nal splitter 56, or single signal 54 B without the signal splitter 56. Broadband white noise is 9 provided by a noise generator 58 and filtered by a low pass filter 60 to provide a white noise signal having a signal ll bandwidth no greater than half of the signal bandwidths l~ provided along the signal path 52, which is to be selectively 13 ~bscured~ Each channel to be selectively controlled is 14 ~ccompanied by a respective local oscillator 62A, 62B and 62C, lS ~hich provide a CW signal at the center frequency of the l~ channel to be selectively obscured. The oscillator signal from 17 aach local oscillator is combined with the band-limited white l~ noise source from the low pass filter 60 in respective . - ; - .-~ 7 ~3~
1 double-balanced mixers 64A, 64B and 64C to provide a translated 2 band-limited white noise signal at a frequency corresponding to 3 the frequencies of the channel to be selectively obscured. The 4 resulting translated white noise is received by an RF switch to selectively place the noise signal on a signal containing the 6 wideband multichannel signal to be distributed. In addition, a 7 plurality of contiguous channels may be obscured by noise by 8 providing an appropriately wider bandwidth filter 60. Each 9 signal drop or user terminal requires as many switches as there 10 are channels to be controlled. In the present embodiment, two ll ~rops are shown, each having three channels to be controlled so 1~ that six RF signal switches 66A-66F are provided.
13 The obscuring of the selected channel is provided by 14 enabling the particular RF switch 66A-66F in response to a control signal derived from signals encoded in the input 16 path 52. The control signal is provided by an encoded signal 1~ rec2ived from the wideband RF signal path 52 by data 18 receiver 68 which provides a baseband coded signal to be 19 processed by the digital processor 70. The resulting control siqnals from processor 70 selectively enable one or more of the ~F switches 66A-66F according to the coded signals provided on the wideband input path S2. The unscrambled channels are ~3 una~ected by the above-described process.
.-. ... ~ .: ... .. . ..
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1 An alternate embodiment is shown in Fig. 2 wherein the multichannel RF signal is received ~rom the path 52 by a signal 3 splitter B2, providing a portion of the received multichannel 4 RF input to a subsequent signal splitter 84, thus providing ._. 5.. .multiple multichannel RF .signals. to.a~plurality of multi-port 6 customer distribution units 86, 88 and 90. The embodiment of 7 Fig. 2 provides an implementation having fewer components by sharing of the local oscillators, mixers, etc. As discussed 9 with the previous embodiment, a plurality of band-limited noise 0 signals of selected frequencies are provided by a white noise 11 generator 58 having a low pass filter 60 thereafter to limit the bandwidth of the noise signal to be limited to half of the 13 signal bandwidth of the channel(s) to be selectively obscured~
14 The resulting band-limited baseband white noise is received by lS double-balanced mixers 64A-64C, which also receive respective 1~ local oscillator CW signals produced by corresponding local 1~ oscillators 62A-62C. The resulting band-lim ted noise signals 18 are received by signal splitt~rs 92, 94 and 96 which provide 19 multiple band-limited noise signals to each of the multi-port customer distribution units 86-90. The signal provided to the customer from each output of the customer distribution units includes the signals corresponding to the multichannel RF input .. , :
:: ,, ~ . ., . :
.: .
~: . ,,,,. , . : , 1 received at input 52, together with the selectively applied 2 band-limited noise signal provided by digitally controlled RF
3 switches located in each multiport customer distribution unit.
4 These and other embodiments, substitutions or _ 5_ modifications made by one skilled in the art are considered to 6 be within the scope of the present invention. For instance, 7 the local oscillators 62A-62C may incorporate a frequency 8 multiplexed frequency synthesizer wherein a single oscillator ~ ~ould be used to jam a plurality of signal channels. Moreover, 1~ tha number of signal drops to user terminals or the number of 11 band-limited signals produced as shown in Figs. l and 2 is 1~ shown for illustration for purposes only, and a greater or 13 lesser number may be provided. Furthermore, through the use of 14 a second baseband noise filter, a wider noise band can be selectively translated to obscure a group of adjacent signal 16 channels. Therefore, the present invention is not to be 17 lim~ted e~cept by the claims which follow.
BACKGROUND OF THE INVEN~ION
Broadband, multichannel signal distribution systems 6 orovide secure channel signal allocation to selected 7 subscribers. In the past, security of the channel information has been provided by two methods, either passive trapping or ~ removal of the channel information, or signal jamming or obscuring the channel information with a secondary signal to 11 make the channel information unusable. In passive trapping, an 1~ electronic band-stop filter is installed in the customer's 13 connection (drop) to eliminate those signals which the customer 14 is not authorized to receive. The passive trap is typically installed at the drop, and may be actuated at the drop either 1~ manually or electronically by a control signal from a remote : .., ~. ., . ;
: .: .. . . . .
~, ~.".,.,i , :. , L~L
1 control point. ~owever, signal traps are subject to frequency 2 drift under changing temperature, and the temperature drift 3 causes the signal trap to drift from the carrier frequency, 4 ~hus allowing unauthorized customer access to the channel.
Moreover, as signal traps tend to be quite wide in bandwidth at 6 higher frequencies, the use of such filters is made 7 economically unfeasi~le or, alternately, makes the adjacent ~ channels also unusable.
9 Signal jamming typically provides a narrow band continuous wave (CW) carrier or modulated carrier which is added to the 11 signal channel of interest. To recover the signal, the 1~ authorized customer is given a narrow band trap to remove the 13 jamming signal. However, the trap used to remove the jamming 14 is also subject to temperature drift. When the drift occurs, a recovered signal could hecome unusable or marginally usable.
16 ~toreover, the trap may remove not only the jamming carrier but 1~ also some of the desired signal, thus degrading the quality of 18 the received signal. Furthermore, since a trap of this nature 19 is installed at the customer location, a customer having electronic knowledge can easily design a device to remove the ~1 jamming signal and thus recover the desired signal without authorization.
~; "
, :; ; ,, ~ . ~ :
-` ~.27~ 4~
SUMMARY OF THE INVENTION
1 The multichannel signal distribution control system 2 according to the present invention completely obscures the 3 selected channel or channels by providing a band-limited noise 4 signal to mask the selected channel signal. Signal parameters S are easily maintained such that the jamming noise signal is limited only to the desired channel or channels, and problems 7 arising due to temperature drift or instability are avoided.
3 ~loreover, the obscured signal is unrecoverable by customer g apparatus since the obscuring signal contains no coded key and is not limited to a narrow frequency band.
11 The apparatus according to the present invention comprises 1~ a baseband noise generator having a noise signal band-limiting 13 ~ilter. T,he resulting band-limited noise source is translated 14 to the channel of interest by a signal translator. Each drop includes at least one signal translator for each secured 1~ channal or group of channels to be controlled. The frequency 1~ translator comprises a local oscillator of a frequency 18 corresponding to the center of the desired channel or group of ~7~3~
1 channels. The local oscillator signal and the baseband signal 2 are received by a balanced mixer to provide the noise source at 3 the selected channel(s) frequency and to suppress the other 4 ~ixer signal components in the mixer output signal. The S -esulting translated.noi.se signal..and a portion of the incoming 6 wideband multichannel signal are combined to provide the user 7 with all signal channels provided by the multichannel ~ distribution system, plus the selected frequency noise jamming 9 signal at the specified channel(s) to be selectively obscured.
The translated noise sources are remotely controlled by a 11 coded signal provided along the multïchannel signal feed from 1~ the home office as received and decoded by a signal decoder and 13 jammer control processor unit.
DESCRIPTION OF THE DRAWING
1~ These are other features according to the present ~nvention will be further understood by reading the following 1~ ~etailed description of the invention, taken together with the 7 drawing wherein:
18 Fig. 1 is a block diagram of one embodiment of the present 9 invention; and , ~, , ~ " . , , , ,, , ~
~'~ 7 ~
1 Fig. 2 is a block diagram of a second embodiment according to the present invention.
DETAILED DESCRIPTION OF THE INVENTION
3 The block diagram of one embodiment of the present 4 invention is shown in Fig. l, wherein the multiple channels of Yideo signals are received from the home office (not shown) 6 along a signal path 52, rom which a plurality of slgnals 54 7 are provided by a si~nal splitter 56, or single signal 54 B without the signal splitter 56. Broadband white noise is 9 provided by a noise generator 58 and filtered by a low pass filter 60 to provide a white noise signal having a signal ll bandwidth no greater than half of the signal bandwidths l~ provided along the signal path 52, which is to be selectively 13 ~bscured~ Each channel to be selectively controlled is 14 ~ccompanied by a respective local oscillator 62A, 62B and 62C, lS ~hich provide a CW signal at the center frequency of the l~ channel to be selectively obscured. The oscillator signal from 17 aach local oscillator is combined with the band-limited white l~ noise source from the low pass filter 60 in respective . - ; - .-~ 7 ~3~
1 double-balanced mixers 64A, 64B and 64C to provide a translated 2 band-limited white noise signal at a frequency corresponding to 3 the frequencies of the channel to be selectively obscured. The 4 resulting translated white noise is received by an RF switch to selectively place the noise signal on a signal containing the 6 wideband multichannel signal to be distributed. In addition, a 7 plurality of contiguous channels may be obscured by noise by 8 providing an appropriately wider bandwidth filter 60. Each 9 signal drop or user terminal requires as many switches as there 10 are channels to be controlled. In the present embodiment, two ll ~rops are shown, each having three channels to be controlled so 1~ that six RF signal switches 66A-66F are provided.
13 The obscuring of the selected channel is provided by 14 enabling the particular RF switch 66A-66F in response to a control signal derived from signals encoded in the input 16 path 52. The control signal is provided by an encoded signal 1~ rec2ived from the wideband RF signal path 52 by data 18 receiver 68 which provides a baseband coded signal to be 19 processed by the digital processor 70. The resulting control siqnals from processor 70 selectively enable one or more of the ~F switches 66A-66F according to the coded signals provided on the wideband input path S2. The unscrambled channels are ~3 una~ected by the above-described process.
.-. ... ~ .: ... .. . ..
: , , ~ ~, : :.: ~ .
:-: -:: , : : : .
~:7~
1 An alternate embodiment is shown in Fig. 2 wherein the multichannel RF signal is received ~rom the path 52 by a signal 3 splitter B2, providing a portion of the received multichannel 4 RF input to a subsequent signal splitter 84, thus providing ._. 5.. .multiple multichannel RF .signals. to.a~plurality of multi-port 6 customer distribution units 86, 88 and 90. The embodiment of 7 Fig. 2 provides an implementation having fewer components by sharing of the local oscillators, mixers, etc. As discussed 9 with the previous embodiment, a plurality of band-limited noise 0 signals of selected frequencies are provided by a white noise 11 generator 58 having a low pass filter 60 thereafter to limit the bandwidth of the noise signal to be limited to half of the 13 signal bandwidth of the channel(s) to be selectively obscured~
14 The resulting band-limited baseband white noise is received by lS double-balanced mixers 64A-64C, which also receive respective 1~ local oscillator CW signals produced by corresponding local 1~ oscillators 62A-62C. The resulting band-lim ted noise signals 18 are received by signal splitt~rs 92, 94 and 96 which provide 19 multiple band-limited noise signals to each of the multi-port customer distribution units 86-90. The signal provided to the customer from each output of the customer distribution units includes the signals corresponding to the multichannel RF input .. , :
:: ,, ~ . ., . :
.: .
~: . ,,,,. , . : , 1 received at input 52, together with the selectively applied 2 band-limited noise signal provided by digitally controlled RF
3 switches located in each multiport customer distribution unit.
4 These and other embodiments, substitutions or _ 5_ modifications made by one skilled in the art are considered to 6 be within the scope of the present invention. For instance, 7 the local oscillators 62A-62C may incorporate a frequency 8 multiplexed frequency synthesizer wherein a single oscillator ~ ~ould be used to jam a plurality of signal channels. Moreover, 1~ tha number of signal drops to user terminals or the number of 11 band-limited signals produced as shown in Figs. l and 2 is 1~ shown for illustration for purposes only, and a greater or 13 lesser number may be provided. Furthermore, through the use of 14 a second baseband noise filter, a wider noise band can be selectively translated to obscure a group of adjacent signal 16 channels. Therefore, the present invention is not to be 17 lim~ted e~cept by the claims which follow.
Claims (4)
PROPERTY OR PRIVILEGE IS CLAIMED ARE DEFINED AS FOLLOWS:
1. A multichannel signal distribution control system for providing a multichannel signal to channels of a subscriber, comprising:
means for distributing said mutlichannel signal to said subscriber, comprising:
a random noise generator providing a band limited random noise signal having a limited bandwidth corresponding to a predetermined portion of the bandwidth of each channel to be selectively obscured;
oscillating means for providing a periodic signal for each channel to be selectively obscured;
means for translating said random noise signal and said periodic signal to produce a translated noise signal to said each channel corresponding to said periodic signal of the respective said multichannel signal distribution control system to be selectively obscured according to a control signal; and means for combining said translated noise signal with said multichannel signal to provide an obscured multichannel signal to said subscriber.
means for distributing said mutlichannel signal to said subscriber, comprising:
a random noise generator providing a band limited random noise signal having a limited bandwidth corresponding to a predetermined portion of the bandwidth of each channel to be selectively obscured;
oscillating means for providing a periodic signal for each channel to be selectively obscured;
means for translating said random noise signal and said periodic signal to produce a translated noise signal to said each channel corresponding to said periodic signal of the respective said multichannel signal distribution control system to be selectively obscured according to a control signal; and means for combining said translated noise signal with said multichannel signal to provide an obscured multichannel signal to said subscriber.
2. The multichannel signal distribution control system of claim 1, further including control means comprising:
a data receiver providing a baseband code signal derived from said multichannel signal;
a code signal processor providing said control signal from said baseband code signal for control of said translating means.
a data receiver providing a baseband code signal derived from said multichannel signal;
a code signal processor providing said control signal from said baseband code signal for control of said translating means.
3. The multichannel signal distribution control system of claim 1, wherein said means for translating comprise:
mixer means for combining said random noise signal and said periodic signal to provide said translated noise signal; and RF switch means for enabling each channel to be selectively obscured in response to said control signal to provide said translated noise signal at said selected channel to be obscured.
mixer means for combining said random noise signal and said periodic signal to provide said translated noise signal; and RF switch means for enabling each channel to be selectively obscured in response to said control signal to provide said translated noise signal at said selected channel to be obscured.
4. The multichannel signal distribution control system of claim 1 wherein said random noise generator is a white noise generator and wherein said random noise signal provided thereby is a white noise signal.
Applications Claiming Priority (2)
| Application Number | Priority Date | Filing Date | Title |
|---|---|---|---|
| US06/923,131 US4825468A (en) | 1986-10-24 | 1986-10-24 | Video noise jammer |
| US923,131 | 1986-10-24 |
Publications (2)
| Publication Number | Publication Date |
|---|---|
| CA1270941A true CA1270941A (en) | 1990-06-26 |
| CA1270941C CA1270941C (en) | 1990-06-26 |
Family
ID=25448173
Family Applications (1)
| Application Number | Title | Priority Date | Filing Date |
|---|---|---|---|
| CA550019A Expired CA1270941C (en) | 1986-10-24 | 1987-10-22 | Video noise jammer |
Country Status (4)
| Country | Link |
|---|---|
| US (1) | US4825468A (en) |
| EP (1) | EP0265349A3 (en) |
| JP (1) | JPS63155891A (en) |
| CA (1) | CA1270941C (en) |
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| JPS60249490A (en) * | 1984-05-24 | 1985-12-10 | Pioneer Electronic Corp | Gate circuit |
| JPS6194480A (en) * | 1984-10-15 | 1986-05-13 | Pioneer Electronic Corp | Generating circuit for jamming signal |
| US4674124A (en) * | 1985-06-06 | 1987-06-16 | Bolt Beranek And Newman Inc. | Multichannel masking sound generator |
-
1986
- 1986-10-24 US US06/923,131 patent/US4825468A/en not_active Expired - Fee Related
-
1987
- 1987-10-22 CA CA550019A patent/CA1270941C/en not_active Expired
- 1987-10-23 EP EP87402402A patent/EP0265349A3/en not_active Withdrawn
- 1987-10-23 JP JP62269147A patent/JPS63155891A/en active Pending
Also Published As
| Publication number | Publication date |
|---|---|
| JPS63155891A (en) | 1988-06-29 |
| EP0265349A2 (en) | 1988-04-27 |
| US4825468A (en) | 1989-04-25 |
| EP0265349A3 (en) | 1990-02-07 |
| CA1270941C (en) | 1990-06-26 |
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Legal Events
| Date | Code | Title | Description |
|---|---|---|---|
| MKLA | Lapsed | ||
| MKLA | Lapsed |
Effective date: 19941226 |