Classifications

• • H—ELECTRICITY
  • H04—ELECTRIC COMMUNICATION TECHNIQUE
  • H04N—PICTORIAL COMMUNICATION, e.g. TELEVISION
  • H04N7/00—Television systems
  • H04N7/16—Analogue secrecy systems; Analogue subscription systems
  • H04N7/167—Systems rendering the television signal unintelligible and subsequently intelligible
  • H04N7/171—Systems operating in the amplitude domain of the television signal
  • H04N7/1713—Systems operating in the amplitude domain of the television signal by modifying synchronisation signals
• • H—ELECTRICITY
  • H04—ELECTRIC COMMUNICATION TECHNIQUE
  • H04N—PICTORIAL COMMUNICATION, e.g. TELEVISION
  • H04N7/00—Television systems
  • H04N7/16—Analogue secrecy systems; Analogue subscription systems
  • H04N7/162—Authorising the user terminal, e.g. by paying; Registering the use of a subscription channel, e.g. billing
  • H04N7/165—Centralised control of user terminal ; Registering at central
• • H—ELECTRICITY
  • H04—ELECTRIC COMMUNICATION TECHNIQUE
  • H04N—PICTORIAL COMMUNICATION, e.g. TELEVISION
  • H04N7/00—Television systems
  • H04N7/16—Analogue secrecy systems; Analogue subscription systems
  • H04N7/167—Systems rendering the television signal unintelligible and subsequently intelligible
  • H04N7/1675—Providing digital key or authorisation information for generation or regeneration of the scrambling sequence
• • H—ELECTRICITY
  • H04—ELECTRIC COMMUNICATION TECHNIQUE
  • H04N—PICTORIAL COMMUNICATION, e.g. TELEVISION
  • H04N7/00—Television systems
  • H04N7/16—Analogue secrecy systems; Analogue subscription systems
  • H04N7/167—Systems rendering the television signal unintelligible and subsequently intelligible
  • H04N7/171—Systems operating in the amplitude domain of the television signal

Definitions

• the present invention relates generally to multichannel television systems and more particularly to interdiction devices for selectively scrambling television channels at subscriber sites.
• Subscription television distribution systems
• providers typically provide a basic block of television channels to subscribers at a subscriber site for a basic monthly fee and one or more premium television channels for additional fees.
• the physical connection itself controls access to the basic channel ⁇ while premium channels are often "scrambled" (encrypted) at their source, i.e., the headend, by the provider to restrict their viewing to only subscribers who pay the additional fee.
• providers may provide unscrambled (in-the-clear) channels to each subscriber site where the provider physically places an interdiction device which blocks, e.g., attenuates or scrambles, selected channels to stop unauthorized subscribers from receiving the selected channels.
• the present invention is directed to a decryption process which facilitates simultaneous decryption of a block of encrypted television channels thus making a decrypted block of television channels simultaneously available for direct tuning by subscriber receivers. Additionally, the present invention is directed to an encryption process which facilitates the jamming of selected television channels from said decrypted block thus making it possible to interdict reception of those selected channels by unauthorized subscribers.
• the present invention can be advantageously used in both over-the-air and hard-wired subscription television distribution systems to provide subscribers with a plurality of simultaneously available decrypted television channels and selectively encrypted channels, e.g., premium channels.
• a system in accordance with the present invention is characterized by a selective interdiction device located at a subscriber site that operates on a block of television channels, decrypted at the subscriber site, such that the interdiction device jams one or more selected channels, e.g., premium, by combining a jamming signal within the frequency range of the channels to be interdicted.
• a selective interdiction device located at a subscriber site that operates on a block of television channels, decrypted at the subscriber site, such that the interdiction device jams one or more selected channels, e.g., premium, by combining a jamming signal within the frequency range of the channels to be interdicted.
• a preferred subscriber site apparatus useful in a system for distributing from a system headend 1 ) multiple channel signals defining an RF band, each channel signal having respective video synchronization components in time coincidence and 2) a common timing reference signal within said band and synchronous with said synchronization components, and wherein each of said channel signals is encrypted in accordance with a common encoding rule comprises a) a timing recovery circuit responsive to said common timing reference signal for generating at least one sync signal, b) a single decoder responsive to said sync signal for simultaneously decrypting all of said channel signals in accordance with the inverse of said encoding rule to generate multiple decrypted channel signals, each capable of directly causing a conventional television receiver to produce an intelligible image, and c) an interdiction apparatus for periodically inserting a jamming signal into at least one of said multiple decrypted channel signals to render it incapable of directly causing said television receiver to produce an intelligible image.
• a preferred subscriber site apparatus useful in a system for distributing from a system headend 1) multiple channel signals defining an RF band, each channel signal having respective video synchronization components in time coincidence and 2) a common timing reference signal within said band and synchronous with said synchronization components, and wherein each of said channel signals is encrypted in accordance with a common encoding rule comprises a) an interdiction apparatu ⁇ for periodically inserting a jamming signal into said RF band to generate an interdicted RF signal, b) a timing recovery circuit responsive to said common timing reference signal for generating at least one sync signal and c) a single decoder responsive to said sync signal and said interdicted RF signal to simultaneously decrypt multiple channel signals in accordance with the inverse of said encoding rule to generate a recovered multichannel signal comprising multiple decrypted channel signals capable of directly causing a conventional television receiver to produce an intelligible image and at least one scrambled channel signal incapable of directly causing said television receiver to produce an intelligible
• Figure IA illustrates that decryption is typically restricted to a single selected channel signal in prior art subscription television distribution systems
• Figure IB illustrates that decryption provides simultaneous access to all encrypted channel signals in a subscription television distribution system in accordance with the present invention
• FIG. 2 illustrates encryption/decryption processes in accordance with the present invention
• Figure ⁇ 3A and 3B are block diagrams of alternative embodiments of an encryption system configured to facilitate the simultaneous decryption of all encrypted channel signals;
• Figure 4 is a block diagram of apparatus for simultaneous decryption of channel signals generated by the system ⁇ of Figures 3A and 3B;
• Figure 5 illustrates a typical composite video signal
• Figure 6A is an enlarged view of the picture and horizontal synchronization components of a plurality of composite video signals,-
• Figure 6B illustrates the composite video signals of Figure 6A with like components in time coincidence
• Figure 6C illustrates an exemplary encoding rule for encoding the components of the composite video signals of Figure 6B;
• Figure 6D illustrates a plurality of encoded composite video signals resulting from modification of the composite video ⁇ ignals of Figure 6B in accordance with the encoding rule of Figure 6C;
• Figure 6E illustrates a plurality of video IF carriers, each amplitude modulated with a different one of the encoded composite video signal ⁇ of Figure 6D;
• Figure 6F illustrates a decoding rule which is the inverse of the encoding rule of Figure 6C;
• Figure 6G illustrates the video IF carriers of Figure 6E after modification in accordance with the decoding rule of Figure 6F
• Figure 7 illustrates the command transmi ⁇ ion ⁇ tructure comprised of multiple data bytes and a reference pulse that are added to a selected channel signal
• Figure 8 illu ⁇ trate ⁇ the relation ⁇ hip of the command transmission structure of Figure 7 to a typical 525 line, 60 HZ television signal;
• Figure 9 illu ⁇ trate ⁇ the relation ⁇ hip of the reference pul ⁇ e to the tenth horizontal ⁇ ync pulse in the televi ⁇ ion signal of Figure 8;
• Figure 10 illustrates the relationship of the command tran ⁇ mission structure of Figure 7 to a typical 625 line, 50 Hz television signal;
• Figure 11 illustrates the relationship of the reference pulse to the eighth horizontal ⁇ ync pulse in the televi ⁇ ion ⁇ ignal of Figure 10;
• Figure 12 is an expanded block diagram of a portion of the proces ⁇ ing of video channel N as shown in Figure 3B;
• Figure 13 is a top level block diagram of an up/down converter embodiment of the data modulator of Figures 3B and 12 ;
• Figure 14 is a detailed block diagram of a preferred up/down converter as shown in Figure 13 ,-
• Figure 15 i ⁇ a block diagram of a preferred embodiment of the decoder portion of the downconverter/decoder a ⁇ shown in Figure 4;
• Figure 16 is a detailed block diagram of an exemplary embodiment of the decoder of Figure 15 ,-
• Figure 17 is a simplified block diagram showing the use of a selective multichannel interdiction device of the pre ⁇ ent invention that ⁇ electively jams predetermined premium channels,-
• Figure 18 i ⁇ a block diagram of a preferred selective multichannel interdiction device that jams predetermined premium channels by adding a jamming ⁇ ignal to each of the ⁇ elected premium channel ⁇ ignal ⁇ ;
• Figure 19 Show ⁇ an exemplary flow chart for a controller that control ⁇ the combining of a jamming signal with the multichannel television signal; and Figure 20 i ⁇ a block diagram of a preferred embodiment of the present invention combining a selective interdiction device with a decoder.
• typical prior art televi ⁇ ion di ⁇ tribution systems provide sub ⁇ cribers with a plurality of encrypted television channel signals 20 but restrict decryption 22 to the production of one decrypted channel signal 24 at a time.
• a ⁇ ub ⁇ criber can cau ⁇ e any one of the encrypted channel signals 20 to be decrypted for viewing on a television set but cannot at the same time record another decrypted channel signal on a video cassette recorder or use another channel signal for a
• one prior art sy ⁇ tem use ⁇ a plurality of decoder ⁇ , e.g., 22A-22N, one for each encrypted channel signal, that respectively decode the channel signal ⁇ which are then upconverted by a plurality of upconverter ⁇ 25A-25N to a new channel frequency 26A-26N.
• Figure IB illustrates that encryption/decryption sy ⁇ tem ⁇ taught by the pre ⁇ ent invention facilitate decryption 28 of all encrypted channel signals 30 simultaneou ⁇ ly ⁇ o that a complete set of decrypted channel signal ⁇ 32 i ⁇ ⁇ imultaneously available in their original frequency slots. Therefore, a subscriber can have each of a plurality of subscriber receivers (e.g., television set ⁇ , video cassette recorders) receiving a different channel signal ⁇ imultaneou ⁇ ly while al ⁇ o u ⁇ ing modern televi ⁇ ion processing features, e.g., picture-in-picture, which require simultaneous availability of multiple channel signal ⁇ .
• subscriber receivers e.g., television set ⁇ , video cassette recorders
• An encryption/decryption proces ⁇ 40 in accordance with the invention, i ⁇ shown in Figure 2.
• Television distribution systems typically include a "headend" where a plurality of television channel signal ⁇ from different sources, e.g., satellite TV signals, standard broadcast VHF and UHF signal ⁇ , are captured, combined and fed into the ⁇ y ⁇ tem.
• headend generation 42 of multichannel televi ⁇ ion ⁇ ignal ⁇ begin ⁇ with a plurality of video sources 44 which each provide a composite video signal 45 including picture and synchronization components (as ⁇ hown in Figure 5 and further described below) .
• the composite video signal ⁇ 45 are encrypted 50 and used to modulate 52 separate channels to place them into separate frequency channels for distribution.
• a process of time synchronization 54 is imposed to place like components of the compo ⁇ ite video ⁇ ignal ⁇ 45 in a predetermined time relation ⁇ hip.
• Di ⁇ tribution 60 to ⁇ ubscriber sites 66 of the channel signal ⁇ generated at the headend may then be accomplished by a variety of well known proces ⁇ e ⁇ , e.g., cable tran ⁇ mission or wireles ⁇ over-the-air transmission, as a common RF signal 68 that contains each composite video signal in a distinct frequency slot.
• the common RF signal 68 comprised of a plurality of television channel signals separated in frequency, arrive at the subscriber site ⁇ 66 in time synchronization so that decryption 70 can be performed on all channel signals simultaneou ⁇ ly.
• Figure 3A show ⁇ a block diagram of a headend 100 in which baseband composite video source ⁇ 102A-102N are each connected to ⁇ eparate electronic delay device ⁇ ⁇ uch a ⁇ frame ⁇ ynchronizers 104.
• the frame ⁇ ynchronizers 104 selectively delay the composite video signals from the sources 102A-102N to place like components, e.g., picture and synchronization components, in time synchronization with reference to a crystal controlled video reference 105, thus generating time synchronized composite video signal ⁇ 106.
• the crystal controlled video reference 105 is coupled to a timing reference generator 108 used to synchronou ⁇ ly generate a common timing reference ⁇ ignal 109, as described further below.
• the time synchronized composite video signals 106 are used to amplitude modulate separate video IF carriers in IF modulators 110 after which encryption i ⁇ accompli ⁇ hed by modifying IF envelopes in accordance with a selected encoding rule (code) in encoders 112, thus generating encoded IF carriers 113.
• Typical apparatus for envelope modification include variable gain amplifiers, variable loss attenuators and selectable signal path ⁇ having different gain ⁇ . Exemplary envelope modification apparatus are disclosed in U.S. Patents 4,706,283; 4,802,214; 4,926,477; and 4,928,309, the disclosures of which are hereby incorporated by reference.
• the modulators 110 and encoders 112 of Figure 3A may alternatively be interchanged, as shown in Figure 3B, to use the encoder 112 to first encode the time synchronized video signals 106 by amplitude modification in accordance with a selected encoding rule and then using the resultant signal to amplitude modulate an IF carrier with the IF modulator 110.
• Video amplitudes may be modified with apparatus similar to the above mentioned examples .
• Specific apparatus for video baseband envelope modification is di ⁇ closed in U.S. Patent 4,928,309, the disclo ⁇ ure of which is hereby incorporated by reference.
• the encoded IF carriers 113 are preferably upconverted from a standard IF frequency and frequency multiplexed in standard television transmitter ⁇ 114 for di ⁇ tribution to ⁇ ub ⁇ criber ⁇ ite ⁇ a ⁇ the common RF ⁇ ignal 68.
• the RF frequency ⁇ lot ⁇ are typically ⁇ pecified in accordance with industry standard ⁇ .
• MMDS Multichannel Multipoint Di ⁇ tribution Service
• MMDS include ⁇ 33 channel ⁇ lot ⁇ within a transmission frequency range of 2500-2686 MHz and 2150- 2162 MHz.
• the timing reference generator 108 generates the common timing reference signal 109 which is transmitted with the synchronized video signal ⁇ to provide master timing information for decoding synchronization.
• This signal is preferably combined with a selected encoded IF carrier 113 to form a data modulated IF carrier 115, by a data modulator 116.
• the data modulator 116 is placed in a selected channel at the headend but it may alternatively be inserted (indicated by broken line) into a transmitter 117 to be carried by an otherwise unused RF channel 118.
• the data modulator 116 may alternatively be present on more than one of the video channels prior to the transmitters 114 and selectively enabled at the headend.
• Authorization data statu ⁇ (de ⁇ cribed further below) i ⁇ al ⁇ o preferably combined with the common timing reference ⁇ ignal 109 and transmitted to selectively enable or disable decoding at each sub ⁇ criber ⁇ ite.
• FIG 4 illustrates a block diagram of a downconverter/decoder 120 suitable for simultaneous decryption at subscriber sites of the common RF signal 68 received from the headend 100 of Figures 3A and 3B.
• downconver ⁇ ion electronic ⁇ 121 are shown essentially comprised of an input RF amplifier 122, a mixer 123 and a local oscillator 124.
• the input RF amplifier 122 amplifies and buffers the common RF signal 68 that was alternatively broadcast or distributed via cable from the transmitters 114 of Figures 3A and 3B.
• the amplifier 122 feeds a buffered common RF signal 126 to the mixer 123 which downconverts the buffered common RF signal 126 using the local o ⁇ cillator 124, generating a downconverted common RF ⁇ ignal 126.
• the common timing reference ⁇ ignal (109 in Figure ⁇ 3A and 3B) i ⁇ recovered in a data/timing receiver 127.
• Specific structure in the receiver 127 for recovery of the common timing reference signal 109 is primarily dependent upon the type of timing signal selected. Exemplary recovery structure ⁇ are di ⁇ clo ⁇ ed in U.S. Patent ⁇ 4,706,283; 4,802,214; 4,926,477; and 4,928,309, previou ⁇ ly referred to above and incorporated herein.
• the data/timing receiver 127 can apply gain control ⁇ ignal ⁇ 128 to a variable gain amplifier/attenuator 130 which ⁇ imultaneously modifies the IF carrier envelopes with signal 126 in accordance with the decoding rule to generate decoded channel signals 132.
• the variable gain amplifier/attenuator 130 is a single element that operates on a single multichannel television signal derived from the common RF signal 68. It is this ability to operate upon all television channel signals by a single element that is referred to in this application as "simultaneous".
• the decoded channel ⁇ 132 are now ⁇ imultaneou ⁇ ly available and can be distributed throughout the sub ⁇ criber site for delivery to multiple sub ⁇ criber receiver ⁇ without further proce ⁇ ing.
• the data/timing receiver 127 preferably confirm ⁇ the authorization data, all channel ⁇ will automatically be available for use, i.e., no user interaction, such a ⁇ ⁇ electing a channel for decoding, will be involved.
• the downconverter/decoder 120 of Figure 4 can be economically integrated to reduce ⁇ ubscriber co ⁇ ts.
• the invention is further disclosed by a preferred proces ⁇ embodiment illustrated in Figures 6A-6G. Description of this exemplary embodiment is facilitated by reference to a typical compo ⁇ ite televi ⁇ ion video ⁇ ignal 220, ⁇ hown in Figure 5, as specified by television industry standards, e.g., National Television Systems Committee (NTSC) .
• the signal 220 of Figure 5 has picture components
• FIG. 6A is an enlarged view of the picture components 222 and horizontal synchronization components 224 of a plurality of compo ⁇ ite video ⁇ ignal ⁇ 220A-220N.
• Each horizontal ⁇ ynchronization component 224 is seen to include a horizontal synchronization pulse 242 and, as in the case of color television, a color bur ⁇ t ⁇ ine wave 244 (indicated by the sine wave envelope) .
• like components of the video signal ⁇ 220 are first aligned in time coincidence as shown in Figure 6B and their amplitude then modified in accordance with a ⁇ elected encoding rule.
• an exemplary encoding rule having an encoding pattern 250 of Figure 6C, will be used.
• the pattern 250 is visually indicated by two lines 251 equally vertically spaced about a centerline 252 in which the vertical spacing between line ⁇ 251 indicate ⁇ gain. Thu ⁇ , the pattern 250 ha ⁇ ⁇ egment ⁇ 253 with a gain 254 interleaved with ⁇ egment ⁇ 255 having a decreased gain 256.
• the encoding pattern 250 is synchronized with the composite video ⁇ ignal ⁇ 220A-220N of Figure 6B to have gain ⁇ egment ⁇ 253 and gain ⁇ egment ⁇ 255 time coincident re ⁇ pectively with picture component ⁇ 222 and horizontal ⁇ ynchronization component ⁇ 224.
• the pattern 250 and the particular time ⁇ ynchronization de ⁇ cribed above are for illu ⁇ trative purpo ⁇ es only; any encoding rule and time synchronization may be used that will prevent unauthorized television receivers from properly displaying the video signal.
• a plurality of encoded video ⁇ ignals 260A-260N is produced having picture components 222' and horizontal synchronization components 224' as shown in Figure 6D. Synchronism between one of the gain segment ⁇ 255 and a corre ⁇ ponding horizontal ⁇ ynchronization component 224" i ⁇ indicated by the broken line ⁇ 266. Thu ⁇ , in the encoded compo ⁇ ite video ⁇ ignal ⁇ 260A-260N, the horizontal ⁇ ynchronization component ⁇ 224 are reduced relative to the other video component ⁇ .
• a plurality of video IF (intermediate frequency) carrier ⁇ 270A-270N have each been amplitude modulated with a different one of the encoded video ⁇ ignals 260A-260N to have amplitude envelopes 271A-271N as shown in broken line ⁇ .
• the modulated video IF carrier ⁇ thu ⁇ have portion ⁇ corresponding to the components of the encoded composite video signals 260 of Figure 6D, e.g., picture portions 272 and horizontal synchronization portions 274 correspond respectively to picture components 222' and horizontal synchronization components 224' .
• the video IF carriers 270A-270N are ⁇ imultaneously shaped in accordance with the inver ⁇ e of the encoding pattern 250.
• Figure 6F illustrates this inverse a ⁇ the decoding pattern 278 in which the gains 254, 256 have been inverted, i.e., segments 255 now have the increased gain 254 while segment ⁇ 253 have the decreased gain 256.
• the decoding pattern 278 is synchronized with the modulated video IF carriers 270 of Figure 6E in the same manner as was done with the encoding pattern 250 of Figure 6C and the composite video signal ⁇ 220 of Figure 6B, i.e., gain ⁇ egment ⁇ 253 and gain ⁇ egments 255 are made time coincident respectively with picture portion ⁇ 272 and horizontal ⁇ ynchronization component ⁇ 274.
• the common timing reference signal may preferably be inserted in synchronization components, i.e., horizontal or vertical, to avoid disturbing picture information.
• the common timing reference signal is preferably combined with authorization data which is coded into one or more video IF carrier signals.
• the illu ⁇ trated preferred method embodiment ⁇ imultaneously decodes modulated IF carriers.
• equivalent method embodiments may include transmi ⁇ ion techniques such as the upconver ⁇ ion of each IF carrier to one of a plurality of RF frequency ⁇ ignal ⁇ followed by frequency multiplexing.
• the re ⁇ ulting RF frequency ⁇ ignals may then be modified in accordance with the inverse of the selected encoding rule to simultaneou ⁇ ly decode the video ⁇ ignal ⁇ carried therein.
• Both IF and RF ⁇ ignal ⁇ may be generically referred to a ⁇ channel ⁇ ignal ⁇ .
• the encryption/decryption process shown in the preferred embodiments has been specifically directed to amplitude modification of analog video signal ⁇
• teaching ⁇ of the invention may generally be extended to encryption/decryption of other forms of video signals, e.g., bit stream ⁇ re ⁇ ulting from digitization of analog video ⁇ ignal ⁇ .
• horizontal sync suppression has been shown a ⁇ an encoding method
• other encoding method ⁇ are also recognized within the scope of the present invention, including vertical sync ⁇ uppre ⁇ ion and horizontal and vertical ⁇ ync ⁇ uppression.
• the illustrated preferred method embodiment aligned corresponding video components in time coincidence for simultaneou ⁇ decryption at ⁇ ub ⁇ criber sites but other embodiments of the invention may synchronize (i.e., place in a predetermined time sequence) corresponding video components for synchronou ⁇ decryption at ⁇ ubscriber ⁇ ite ⁇ .
• the basic structure of the authorization data is preferably comprised of twelve data bytes, divided into two data blocks 300 and 302 of six bytes each, corre ⁇ ponding to the two interlaced field ⁇ which form a ⁇ ingle video frame and a preci ⁇ ely placed reference pulse 304 used to provide timing information for decrypting the common RF signal 68. Additionally, start sequences 306 and 308 are provided to identify the start of each data block. The data bytes are preferably used to identify authorized individuals or groups of authorized subscribers to the otherwise encrypted service.
• one byte i ⁇ preferably included a ⁇ a validity check byte 310 for the authorization data. Additionally, the validity check byte 310 may be used to determine valid receive timing synchronization.
• a video frame is comprised of 525 interlaced horizontal lines of video information divided into two fields at a 30 Hz frame rate. The beginning of each field is signified by vertical sync components 312 and 314, defining a vertical synchronization interval, that cause a vertical retrace during which the screen is blanked. Video information need not be present during the vertical synchronization interval since the screen is blanked.
• a preferred embodiment use ⁇ the vertical ⁇ ynchronization interval, defined by vertical sync components 312 and 314 and comprised of multiple horizontal lines, to transmit the authorization data without interfering with the displayable video information.
• Transmis ⁇ ion of the fir ⁇ t data block 300 comprised of the first start sequence 306, a first set of data bytes 318, six data bytes in a preferred embodiment, and the reference pulse 304, begins with the time period defined by the first horizontal line 316.
• the reference pul ⁇ e 304 i ⁇ preci ⁇ ely ⁇ ynchronized with a horizontal ⁇ ync pul ⁇ e 320 that follow ⁇ the tenth horizontal line 322.
• the transmission period for the first data block 300 is contained within the time period for horizontal line ⁇ 1-10, a ⁇ ⁇ hown in Figure 8.
• thi ⁇ data is defined as a combination of bits comprised of marks, i.e., "l”s or “high”s, and space ⁇ , i.e., "0" ⁇ or “low” ⁇ .
• marks i.e., "l”s or "high”s
• space ⁇ i.e., "0" ⁇ or "low” ⁇ .
• start sequences 306 and 308 are used in combination with the validity check byte 310 to define detection periods corresponding to horizontal lines 1-10 and 263-272.
• the start sequence ⁇ 306, 308 are each defined by a memori ⁇ of unique data bits, all "l"s in a preferred embodiment.
• Each data byte within the fir ⁇ t and ⁇ econd ⁇ ets of data bytes, respectively 318 and 324, are preferably transmitted as 8-bit characters according to a conventional 11-bit asynchronou ⁇ protocol, a ⁇ shown in Figure 9, with one low ⁇ tart bit 325 and two high ⁇ top bit ⁇ 326 per character.
• a ⁇ i ⁇ common with a ⁇ ynchronou ⁇ character tran ⁇ mission protocols, the time each character is transmitted is not precisely fixed in time.
• a transmission rate is chosen that permits the transmis ⁇ ion of an 11-bit start sequence 306, six 11-bit characters 318 and ⁇ till provide ⁇ ufficient time to preci ⁇ ely place the reference pul ⁇ e 304 in ⁇ ynchronization with the horizontal sync pulse 320 following the tenth horizontal line 322.
• a bit rate of 140,625 bps is used.
• the reference pulse 304 is de ⁇ cribed here in reference to a particular video signal, e.g., 220B, it should be recognized that since all of the video signal ⁇ 220A-220N are synchronized by frame synchronizers 104, the reference pulse 304 will be precisely synchronized to the horizontal sync pulse following the tenth line for all of the video signals.
• a particular video signal e.g., 220B
• the reference pulse 304 will be precisely synchronized to the horizontal sync pulse following the tenth line for all of the video signals.
• a first data block 327 is placed within horizontal lines 624 and 9 and a second data block 328 is placed within horizontal lines 311 and 320.
• the reference pulse 330 is precisely placed in synchronization with the horizontal sync pulse following the eighth line 332.
• the television channel ⁇ elected for transmitting the authorization data is fixed, e.g., always set to a predetermined channel N.
• the downconverter/decoder 120 is preferably configured to scan channels within its frequency range to identify the channel containing the authorization data. Alternate embodiments may alter the data channel selection according to a predetermined algorithm, e.g., a different channel for each time period, a first data channel identifies a next data channel, etc.
• the common timing reference signal 109 can alternatively be coupled to any one or all of a plurality of data modulators 116.
• a ⁇ elect ⁇ ignal (not ⁇ hown) can optionally enable a particular data modulator 116 to add the common timing reference ⁇ ignal 109 to a selected channel.
• Figure 12 there is shown an expanded block diagram of a portion of the encryption proces ⁇ ing of video channel N, as shown in Figure 3B, showing the interface of the encoder 112N and the IF modulator 110N to the data modulator 116.
• the encoder 112N applie ⁇ a ⁇ elected encoding rule, e.g., removing the horizontal and vertical ⁇ ynchronizing component ⁇ 224, 226 from a time ⁇ ynchronized video ⁇ ignal 106N, to di ⁇ able subscribers without authorized decoders from receiving a video channel.
• An encrypted video signal 334 is then modulated by the IF modulator 110N, generating the encoded IF carrier 113N.
• the encoded IF carrier 113N from the IF modulator 110N is modulated by the data modulator 116 during the time period corresponding to the vertical synchronizing component 226, i.e., the vertical synchronization interval, in respon ⁇ e to the common timing reference signal 109 and sent via the data modulated IF carrier 115 to the transmitter 100N.
• the data modulator 116 is only present on a selected channel 1-N in a preferred embodiment. In another embodiment, the data modulator 116 may be present for all N channels but may be enabled only for the selected channel or alternatively for a plurality of channels. Alternatively, a single data modulator 116 may be switched to the selected channel.
• the timing reference generator 108 under control of a microcontroller 340, generates the common timing reference signal 109 in synchronism with a clock 342 received from the crystal controlled video reference 105.
• the common timing reference ⁇ ignal 109 additionally preferably compri ⁇ e ⁇ the authorization data for specifying authorized subscriber .
• Authorization information i ⁇ maintained in a system controller (not shown) and communicated via signal path 344 to the microcontroller 340 where it is formatted a ⁇ the authorization data onto the common timing reference ⁇ ignal 109.
• the common timing reference ⁇ ignal 109 contain ⁇ three data ⁇ tate ⁇ corre ⁇ ponding to no data, a mark and a space, thus causing the data modulator 116 to alter the encrypted IF signal 113 on receipt of a mark or space but leave the encrypted IF signal 113 unaltered when receiving a third, no data, state signal.
• the cry ⁇ tal controlled video reference 105 deliver ⁇ a sync signal 346 to the data modulator 116 to enable data modulation only during the vertical synchronization interval.
• the data modulator 116 u ⁇ e ⁇ FSK (frequency ⁇ hift keying) to modulate the encoded IF carrier 113 of a ⁇ elected MMDS channel with the authorization data and the reference pul ⁇ e 304 during the vertical ⁇ ynchronization interval.
• the data modulator 116 receive ⁇ the common timing reference ⁇ ignal 109, compri ⁇ ed of the reference pul ⁇ e 304 and the authorization data comprised of set ⁇ of data byte ⁇ 318 and 324 u ⁇ ed to authorize or deauthorize each ⁇ ubscriber.
• the outputs of the data modulator 116 are the audio and video carriers, FM modulated with the set ⁇ of data byte ⁇ 318 and 324 and the reference pul ⁇ e 304 during the vertical ⁇ ynchronization interval.
• the preferred data modulator 116 is characterized by: 1) the difference between the output frequencies of the modulated carriers are the same as their respective input carrier frequencies, 2) the sy ⁇ tem should not add noise or distortion to the modulated carriers, and 3) the audio and video carriers should match in deviation and phase. Since the audio carrier is typically produced as a beat frequency between the audio and video IF carriers, if the audio and video IF carriers do not match in phase and maintain the frequency difference of the original carriers, an unwanted hum could be produced.
• the encoded IF carrier 113 is comprised of a separate video IF carrier 350 and audio IF carrier 352.
• the video IF carrier 350 and the audio IF carrier 352 are typically at 45.75 MHz and 41.25 MHz, respectively, and are nominally separated in frequency by 4.5 MHz.
• the reference IF carrier 353, generated by the up/down converter 348, is comprised of a separate video carrier+data signal 354 and audio carrier+data signal 356, both of which are uniformly FSK modulated in respon ⁇ e to the common timing reference signal 109.
• the data respon ⁇ ive frequency deviation for the carrier ⁇ 350 and 352 is ⁇ 25 KHz.
• FIG 14 a detailed block diagram of a preferred up/down converter 348 is shown.
• the up/down converter 348 con ⁇ ists of a two pairs of mixers 358, 360 and 362, 364, one pair for each carrier, i.e., video 350 and audio 352, under control of a common pair of local oscillators.
• First and second oscillator ⁇ 366 and 368 are VCO ⁇ (voltage-controlled o ⁇ cillator ⁇ ) pha ⁇ e locked to a common cry ⁇ tal o ⁇ cillator 370.
• the fir ⁇ t o ⁇ cillator 366 function ⁇ as a local oscillator (LO) 372 to mix each carrier up to an intermediate frequency and the second oscillator 368 function ⁇ a ⁇ a ⁇ econd local oscillator 374 to mix the signal back down to it ⁇ original IF frequency.
• the second local oscillator 374 is frequency modulated with the data from the common timing reference signal 109. Since the second local oscillator 374 changes frequency in response to the common timing reference signal 109, the downconverted carriers 354 and 356 al ⁇ o change frequency and additionally contain FSK data providing ⁇ ynchronization and the authorization data.
• the second local oscillator 374 used for the second downconversion is frequency modulated as follows.
• the phase locked loop of the VCO 368 is used in the second downconversion.
• the common timing reference signal 109 is summed onto a control line 376 of this VCO 368. Since the modulated VCO 368 is used a ⁇ the local o ⁇ cillator 374 for the downconver ⁇ ion, the RF carriers 354 and 356 are also modulated and thus contain the FSK data.
• the audio and video carriers are separate and thus, this same process is performed in parallel on both the video and audio carriers 350 and 352 using the ⁇ ame two local o ⁇ cillators 372 and 374.
• Signals from each oscillator 372, 374 are split and respectively sent to two mixers 358, 362 and 360, 364.
• the audio carrier 352 is upconverted u ⁇ ing the first local oscillator 372 and then downconverted to the original IF frequency using the FM modulated second local oscillator 374. Since the same frequency modulated local oscillator 374 is used in the downconversion of the audio and video carriers, the frequency deviation of both carriers will be es ⁇ entially identical.
• the decoder portion 400 receive ⁇ the downconverted common RF ⁇ ignal 126, recover ⁇ the common timing reference ⁇ ignal 109 contained within u ⁇ ing the data/timing receiver 127, and in response generates gain control signals 128 to instruct the gain amplifier/attenuator 130 to operate upon the downconverted common RF signal 126 according to the inverse of the selected encoding rule, e.g., reinserting horizontal and vertical components, to generate the decoded channel ⁇ signal 132.
• the decoded channels signal 132 can be distributed to one or more standard television receivers which can independently receive one or more decoded television channels.
• the data/timing receiver 127 is preferably comprised of a superheterodyne dual conversion FSK data receiver 402 under control of a controller 404.
• the controller 404 receives a decoded data output signal 406 from the data receiver 402 and generates frequency control signal ⁇ to pha ⁇ e lock the data receiver 402 to the decoded data output signal 406.
• the data/timing/receiver 127 preferably comprise ⁇ an input attenuator 408 that accept ⁇ the downconverted common RF signal 126 and, under control of the controller 404, generate ⁇ a common attenuated signal 410 to the data receiver 402 and the gain amplifier/attenuator 130.
• the controller 404 additionally receives a receive signal ⁇ trength indicator (RSSI) 412 from the data receiver 402 and responsively generates an attenuation control signal 414 to the input attenuator 408.
• the controller additionally generates gain control signal ⁇ 128 to the gain amplifier/attenuator 130 compri ⁇ ed of a blanking control line 416 and a ⁇ ync control line 418.
• the ⁇ e control lines are used for reinserting the vertical and horizontal sync signals, respectively, into the common attenuated signal 410 derived from the downconverted common RF signal 126.
• the data receiver's 402 principal purpose is to retrieve the common timing reference signal 109 from a selected channel within the common attenuated signal 410 and to deliver the common timing reference signal 109 as the decoded data output signal 406, representative of the authorization data and the precisely timed reference pulse 304.
• the data receiver 402 is comprised of a first IF 420, a second IF 422 and a data detector 424.
• the first IF 420 receives the common attenuated signal 410, typically having a frequency range of 222 to 408 MHz corresponding to CATV channels 24 to 54, and downconverts the ⁇ elected channel to a fixed frequency first IF output signal 426.
• the ⁇ econd IF 422 then further downconvert ⁇ the fir ⁇ t IF output ⁇ ignal 426 to a fixed frequency ⁇ econd IF output ⁇ ignal 428.
• the second IF output signal 428 i ⁇ input to the data detector 424 which extract ⁇ the decoded data output signal 406 and the receive signal strength indicator 412.
• the channel selection is determined by the controller 404 by ⁇ canning the available channels for data. To scan the available channels, the controller 404 generate ⁇ a channel select signal 430 to the first IF 420 which determines the amount of frequency downconversion required for the common attenuated signal 410.
• the channel select signal 430 is iteratively altered until data is succe ⁇ fully received.
• the controller 404 generate ⁇ a second IF frequency select signal 432 to the second IF 422.
• the operating frequencies of the first IF 420 and the second IF 422, as determined by the channel select 430 and second IF frequency select 432 signals are adjusted by the controller 404 in respon ⁇ e to the decoded data output signal 406, thus phase locking the data receiver 402 to the data contained within, i.e., the common timing reference signal 109.
• Figure 16 show ⁇ a detailed block diagram of an exemplary embodiment of the decoder 400 of Figure 15, comprised of the first IF 420, the second IF 422 and the data detector 424, that ⁇ end ⁇ data to the controller 404 that in turn controls the gain amplifier/attenuator 130, comprised of two switchable RF attenuator ⁇ , to re-in ⁇ ert ⁇ ync and blanking signals directly on cable television frequencies.
• the gain amplifier/attenuator 130 comprised of two switchable RF attenuator ⁇ , to re-in ⁇ ert ⁇ ync and blanking signals directly on cable television frequencies.
• video channels contained within the downconverted common RF signal 126 do not contain horizontal or vertical sync pulses.
• the horizontal blanking level corresponding to each channel within the common RF signal 68 is preferably attenuated to prevent detection circuitry of some television receivers from using the blanking signal as a false sync reference.
• the blanking level is not attenuated by the encryption.
• the decoder 400 perform ⁇ the inverse of the selected encoding rule to restore the sync and blank signals to proper levels using a pair of two level RF attenuator ⁇ , a blanking ⁇ witch 434 and a sync switch 436.
• An amplifier 438 isolate ⁇ the blanking and ⁇ ync switches 434, 436 to prevent signal interactions.
• the amplifier 438 is preferably a linear amplifier capable of handling multiple high level carriers with low distortion.
• a pad 440 helps to isolate the ⁇ ync ⁇ witch 436 from poor external impedance matching.
• the input attenuator 408 is activated when the downconverted common RF signal 126 reaches a certain level. This prevents distortion of both the gain amplifier/attenuator 130 and the data/timing receiver 127.
• the receive signal strength indicator 412 generated by the data detector 424, provides information for the controller 404 to determine at what level to ⁇ witch in the input attenuator 408 via the attenuator control ⁇ ignal 414.
• a resistive splitter 442 provides a signal to both the gain amplifier/attenuator 130 and the fir ⁇ t IF 420.
• the re ⁇ i ⁇ tive splitter 442 also help ⁇ to i ⁇ olate and prevent interaction with the input attenuator 408.
• the data receiver front end include ⁇ a high i ⁇ olation amplifier 444 to i ⁇ olate a fir ⁇ t local o ⁇ cillator 446.
• a pad 448 at the input of the amplifier 444 prevent ⁇ di ⁇ tortion of the amplifier 444 from the multiple carrier ⁇ within the downconverted common RF signal 126.
• a pad 450 at the output of the amplifier 444 provides an ea ⁇ y broadband match to the input of a fir ⁇ t mixer 452 and also prevent ⁇ distortion. Both attenuators 448 and 450 also help i ⁇ olate the first local oscillator 446.
• the 446 combination provide a programmable local oscillator frequency range.
• the data carrier can be any of the video carriers in this band.
• the IF frequency is preferably chosen to avoid mixing of carriers within the frequency range.
• a frequency synthesizer 454 keeps the first local oscillator 446 in phase lock while receiving a reference frequency from the controller 404.
• the frequency synthe ⁇ izer 454 is preferably capable of tuning the first local oscillator 446 using the channel select signal 430 from the controller 404.
• the controller 404 iteratively tunes the first local o ⁇ cillator 446 until data i ⁇ ⁇ ucce ⁇ sfully received.
• the controller 404 is preset to a value for tuning the first local oscillator 446.
• a pad 455 follows the first mixer 452 to prevent overloading a second mixer 456 as well as to provide a good input termination for an image filter 458.
• the second IF 422 is chosen to produce and demodulate an IF frequency, e.g., 10.7 MHz, for which ceramic bandpas ⁇ filter ⁇ are readily available.
• a ⁇ econd frequency ⁇ ynthe ⁇ izer 460 identical to the fir ⁇ t frequency synthesizer 454, is used to phase lock a second local oscillator 462.
• a first ceramic filter 464 follows the second mixer 456 and set ⁇ the demodulation bandwidth.
• An IF amp 466 follow ⁇ the first ceramic filter 464 and helps to limit the signal.
• a ⁇ econd ceramic filter 468 follow ⁇ the IF amp 466 for additional band ⁇ haping.
• a gain limiter amplifier 470 follow ⁇ the second ceramic filter 468 for hard limiting.
• a quadrature detector 472 follows the limiter amplifier 470 and demodulates the FSK data.
• the input signal preferably deviates ⁇ 25 KHz and has a data rate of 140,625 bits per second.
• Demodulated data from the quadrature detector 472 enters a data slicer 474 where uncertain data edges are cleaned up, made absolute and fed to the controller 404 as the data output signal 406.
• the controller 404 In order to perform the inverse of the selected encoding rule, e.g., to insert the sync and blanking signal ⁇ , at precisely the correct position in time, the controller 404 is phase locked to the time reference provided from the synchronized signals at the headend. This time reference, originally generated from the common timing reference signal 109 at the headend, become ⁇ available to the controller 404 as part of the demodulated data signal 406.
• the controller 404 performs the inverse of the selected encoding rule with a sync and blank generator that locks itself to the edge of a received reference pulse to avoid sync drift. In a preferred embodiment, this locking is accomplished by altering the clock frequency of the controller 404.
• the controller 404 i ⁇ comprised of a proces ⁇ or 476, preferably a microcontroller, executing software at a rate controlled by a voltage controlled crystal oscillator 478.
• the processor 476 sends a feedback signal 480 to a digital to analog converter 482 which drives the voltage controlled crystal oscillator 478 and effectively changes the clock frequency and thus the execution speed of the processor 476.
• the channel select 430 and the second IF frequency select signals 432 are thus responsively altered, phase locking the data receiver 402 to the decoded data signal 406.
• the controller 404 As discussed in reference to the data modulator 116, data is only sent during prescribed periods, the vertical synchronization intervals.
• the controller 404 under ⁇ oftware control, recognize ⁇ the reference pulse 304, and a combination of the first start sequence 306, the second start sequence 308 and the validity check byte 310, to ensure that the controller 404 is ⁇ ynchronized with the common timing reference ⁇ ignal 109.
• the controller 404 alter ⁇ its clock frequency and/or the time window during which it looks for the data block ⁇ 300 and 302.
• encryption/decryption method and apparatu ⁇ embodiment ⁇ have been di ⁇ clo ⁇ ed herein which make a plurality of distributed television channels ⁇ imultaneou ⁇ ly and automatically available to authorized ⁇ ub ⁇ criber ⁇ . Additionally, a single channel system using the di ⁇ closed modulation and demodulation methods is also considered within the scope of the present invention.
• the previously disclosed invention can advantageously ⁇ imultaneou ⁇ ly decode a block of televi ⁇ ion channel ⁇ ignal ⁇ .
• the pre ⁇ ent invention u ⁇ es an interdiction device to selectively scramble television channel signals from within the block of locally decrypted channel signal ⁇ .
• Figure 17 ⁇ how ⁇ the u ⁇ e of a preferred interdiction device 510 which selectively jams a multichannel television (TV) channel signal 512, an unencrypted signal, from a typical prior art television distribution sy ⁇ tem (not ⁇ hown) to generate a ⁇ ignal 514 to provided ⁇ ub ⁇ criber ⁇ with a plurality of unencrypted televi ⁇ ion channel ⁇ ignal ⁇ a ⁇ well as a plurality of ⁇ electively encrypted/jammed channel ⁇ ignals. While ⁇ uch a ⁇ y ⁇ tem can be u ⁇ ed in various environments, e.g., over-the-air and conventional cable subscriber systems, it is particularly useful in combination with the previously disclosed decoder 400.
• TV television
• sy ⁇ tem not ⁇ hown
• the interdiction device 510 is programmable and capable of selectively scrambling a plurality of television channel ⁇ throughout the range of otherwi ⁇ e unencrypted televi ⁇ ion channel ⁇ from ⁇ ignal 512.
• Figure 18 shows a block diagram of the preferred mterdiction device 510.
• Embodiments of the present invention are based upon the recognition that television channels are allocated separate frequency slot ⁇ , ⁇ eparated by fixed amount ⁇ , e.g., 6 or 8 MHz. If a jamming ⁇ ignal is properly isolated to a fixed channel, only that channel is disrupted/jammed without significantly effecting even adjacent channels.
• the preferred interdiction device 510 primarily comprise ⁇ : 1) a frequency synthesizer/VCO 516 (a jamming ⁇ ignal generator) for generating a jamming signal, e.g., an FM-modulated sine wave, 2) a controller 518 for directing the frequency synthesizer/VCO 516 to generate a jamming, signal 520 for a selected television channel, 3) a mute switch 522 under control of the controller 518 for only enabling the output of the jamming signal 520 when the frequency synthe ⁇ izer/VCO 516 ha ⁇ locked to a predetermined jamming frequency for each selected channel, and 4) a summer 524 for combining the multichannel television channel signal 512 and the generated jamming signal 520 passed by the mute switch 522.
• a frequency synthesizer/VCO 516 a jamming ⁇ ignal generator
• a controller 518 for directing the frequency synthesizer/VCO 516 to generate a jamming, signal 520 for
• the controller 518 contains a channel interdiction table 526, which corresponds to the preselected channels that are to be jammed. Each of these channels correspond to specific frequencies for each geographical area, e.g., USA, Europe, etc., and to particular transmis ⁇ ion standards, e.g., NTSC or PAL. (See, e.g., Table I below depicting frequency assignment ⁇ for a VHF Sy ⁇ tem M (6 MHz) USA.)
• a ⁇ econd table (not shown) within the controller 518 is preferably used to convert each channel designation to its corresponding frequency.
• table 526 may directly contain frequency designation ⁇ corre ⁇ ponding to the ⁇ elected channel ⁇ .
• the table 526 may alternatively be preloaded, e.g., ⁇ tored in nonvolatile memory, or may be loaded via communication between the controller 518 and ⁇ ome external device, e.g., via a communication interface 527.
• the multichannel televi ⁇ ion ⁇ ignal 512 can contain authorization data via the communication interface which can be decoded to instruct identified controllers 518 to add or delete entries from its channel interdiction table ⁇ 526.
• the controller 518 command ⁇ the frequency synthesizer/VCO 516 via a control interface 528 comprised of a frequency select bus 530 (used to select the desired jamming frequency corresponding to a selected channel) and a lock signal 532 (used to provide a feedback statu ⁇ signal) .
• the frequency synthesizer/VCO 516 takes a di ⁇ crete, i.e., a nonzero, amount of time (a function of the de ⁇ ign of the frequency synthe ⁇ izer/VCO 516) to lock to the de ⁇ ired jamming frequency. Once the de ⁇ ired jamming frequency i ⁇ achieved, the jamming frequency is preferably maintained for a period of time before a next jamming frequency is selected.
• the lock signal 532 is then generated by the frequency synthe ⁇ izer/VCO 516 which can be u ⁇ ed to notify the controller 518 that the de ⁇ ired jamming frequency ha ⁇ been achieved.
• the lock ⁇ ignal 528 i ⁇ generated by a frequency comparator within the frequency ⁇ ynthe ⁇ izer/VCO 516 which compares the jamming signal 520 to the frequency commanded by the controller 518.
• the controller 518 in block 542 in ⁇ tructs the mute switch 522 via the mute control signal 534 to commence jamming the selected television channel.
• the controller alternatively waits a predetermined time period or waits for the lock signal 532 to be returned from the frequency synthe ⁇ izer/VCO 516.
• the output of the mute ⁇ witch 522 must be maintained during block 544 for a sufficient time period, e.g., at least one frame period, to adequately jam the selected television channel.
• the controller in block 546 enables the mute ⁇ witch 522 via the mute control signal 534 (if the next channel to be interdicted is not adjacent to the current channel) .
• the process then cyclically repeats, starting at block 538, with the next entry in the channel interdiction table 526.
• a first time period related to the lock time in block 540 and a second time period defined by the predefined time period in block 544 there are two time periods involved in this cyclical process, a first time period related to the lock time in block 540 and a second time period defined by the predefined time period in block 544. Accordingly, there is a maximum cycle rate (for a particular implementation) , that this process can be repeated. This cycle rate determines the maximum number of channels (five in an exemplary embodiment) that can continuously (as viewed by a subscriber) be interdicted. Accordingly, in an alternative embodiment, a plurality of frequency synthesizer/VCOs 516 are multiplexed such that one can be approaching its jamming frequency (in block 540) while another is dwelling at its jamming frequency (in block 544) .
• Figure 18 additionally ⁇ how ⁇ the ba ⁇ ic ⁇ tructure of the preferred frequency synthesizer/VCO 516 which is primarily comprised of 1) a video frequency synthesizer 548, 2) an audio frequency synthe ⁇ izer 550, 3) a summer 552, and 4) a VCO 554 (voltage-controlled oscillator) .
• the video frequency synthe ⁇ izer 548 e.g., a National LMX1511A or Fujit ⁇ u MB15A02, is commanded to select a particular frequency, e.g., the base video carrier frequency of the television channel offset by a jam frequency, e.g., a frequency approximately half way through the television channel or approximately 3 MHz, via the three wire bus 530 comprised of clock, data, and enable signals (an interface particularly well- suited for sharing with additional frequency synthe ⁇ izer ⁇ ) .
• the frequency synthesizer 548 generates an analog video VCO control signal 556 that commands the VCO 554 to generate the desired frequency.
• a feedback signal 558 is returned to the frequency synthe ⁇ izer 548 where it is compared in frequency with the frequency commanded by the controller 518. When a match is achieved the lock signal 532 results and this status signal is communicated to the controller 518.
• the frequency synthesizer/VCO 516 would be tunable to the entire potential frequency range, e.g., 40-860 MHz, or more. Practically, this goal may not be easily achievable. Thus, in an exemplary embodiment the frequency synthesizer/VCO 516 is tunable between 260-422 MHz, corresponding to television channels 31-55.
• Channel 44 has a video carrier of 343.25 MHz with the preferred jamming frequency at 346.25 MHz (343.25 MHz plus a preferred offset of 3 MHz).
• the preferred jamming frequency of channel 50 is at 382.25 MHz (379.25 MHz plus a preferred offset of 3 MHz).
• a preferred embodiment additionally comprises the audio frequency synthesizer 550, which in an exemplary embodiment divides a frequency output 560 of the frequency synthesizer 548 to generate a digital audio VCO control signal 562.
• the analog video VCO control signal 556 and the digital audio VCO control signal 562 are summed by summer 552 to generate a VCO control signal 564 which controls the VCO 554 to generate a frequency-modulated jamming signal that will jam both the video and audio portions of the selected television channel.
• Figure 20 shows a preferred embodiment of the present invention comprised of the multichannel interdiction device 510 combined with the previously disclosed decoder 400. While the prior decoder 400 disclosed significant improvements over the prior art by permitting a single apparatus to simultaneously decrypt all or none of the transmitted channels according to transmitted authorization data, it did not permit the provider to restrict access to selected channels. With the present decoder/interdiction device combination 566, the microcontroller 518 receives authorization data from a data receiver 568 via its data output 570 that has been inserted at the headend to identify authorized subscribers (preferably identified with a predefined subscriber or box code in the microcontroller 518) .
• the same microcontroller 518 that controls the common decrypting of a commonly encrypted input source 572 loads the channel interdiction table 516 according to the authorization data, e.g., according to tier ⁇ .
• the data in the interdiction table 516 i ⁇ then u ⁇ ed to control the operation of the frequency ⁇ ynthe ⁇ izer/VCO 516 and the mute ⁇ witch 522 u ⁇ ing the control interface 528 and mute control ⁇ ignal 534 according to the previously described algorithm.
• This improved combination now permits the simultaneou ⁇ reception of multiple unencrypted ⁇ ignals (suitable for picture-in-picture use) while still permitting the provider to withhold access to selected channels.
• a standardized jamming amplitude ratio be achieved between the jamming signal at the mute switch output 536 and the multichannel television channel signal 512. Without this standardization, undesirable results could occur. For example in a first mode, one might attempt to pirate a jammed television signal by amplifying the common scrambled input source 572 to overcome the jamming signal. However, if a standardized jamming amplitude ratio is maintained, the input source 572 would automatically be attenuated and this pirating attempt would fail. Conversely in a ⁇ econd mode, if an abnormally small input source 572 should be present, a proportionally large jamming signal could tend to spill over and effect adjacent channels.
• a receive signal strength indicator (RSSI) 574 from the data receiver 568, indicative of the amplitude of the commonly scrambled input source 572 is used to control an AGC amplifier 576 to standardize the amplitude of a common attenuated signal 578 operated on within the decoder 400.
• RSSI receive signal strength indicator
• an AGC amplifier could be used to control the amplitude of the jamming frequency.
• authorization data is generally sent on a predetermined authorization data channel .
• the predetermined channel can be varied to further limit pirating.
• a preferred channel interdiction table can be structured to take advantage of these embodiments .
• a first entry for each channel correspond ⁇ to a delta frequency from the authorization data channel frequency and a ⁇ econd entry ⁇ pecifie ⁇ whether this channel is to be interdicted.
• a pirate would need to know at least the present authorization data channel, any scheme for varying the authorization data channel, and the data within the interdiction table.
• pirating is further complicated.
• the present decoder / interdiction device 566 can simultaneou ⁇ ly decode all of the tran ⁇ mitted channel ⁇ by rever ⁇ ing the encoding proce ⁇ done to a plurality of ⁇ ynchronized channels.
• this encoding is done by first synchronizing a plurality of video inputs at the headend and then suppressing the horizontal and vertical sync signal of the synchronized video inputs. Consequently, once the microcontroller determines the proper timing, a blanking control line 584 and sync control line 586 can simultaneously decode all of the received channels to generate the multichannel television channel signal 512, the input signal to the interdiction device 510.
• the pre ⁇ ent invention can take advantage of this relationship to optimize its temporal placement of the jamming signal 520 within each channel frequency range. Therefore, in this embodiment the predefined period of block 544 i ⁇ preferably defined by thi ⁇ known timing relationship; permitting the single frequency synthesizer/VCO 516 to jam a larger number of television channels.
• the present invention can also be used with an unscrambled over-the- air system, e.g., a microwave signal after a downconverter that provides an unscrambled multichannel television signal.
• an unscrambled over-the- air system e.g., a microwave signal after a downconverter that provides an unscrambled multichannel television signal.
• interdiction/jamming step can precede the simultaneou ⁇ decrypting step with similar result ⁇ .

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• Two-Way Televisions, Distribution Of Moving Picture Or The Like (AREA)

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• 1995
  • 1995-12-21 BR BR9510615A patent/BR9510615A/pt not_active Application Discontinuation
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  • 1995-12-21 AU AU46450/96A patent/AU4645096A/en not_active Abandoned
  • 1995-12-21 EP EP95944387A patent/EP0806116A4/de not_active Withdrawn
  • 1995-12-21 WO PCT/US1995/016827 patent/WO1997003523A1/en not_active Application Discontinuation
• 1998
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