Network system for handling digital data over a TV channel

A method of transmitting digital data in a television channel without disturbing television transmission quality wherein said channel carries a conventional television signal that includes audio, video and synchronizing information, said method comprising:

• modulating a carrier signal with representations of data from a digital data stream thereby to generate said supplemental data signal,
• generating upper and lower sidebands of said television signal wherein one of said sidebands includes a vestigial sideband of said television signal,
• removing a portion of said vestigial sideband and substituting therefor a representation of said supplemental data signal,
• deriving synchronizing information from a residual portion of at least one of said sideband,
• transmitting a modified television signal that includes a representation of said supplemental data signal, said residual synchronizing information, and said television signal,
• receiving said modified television signal at a receiver,
• extracting a synchronizing signal from a sideband of said modified television signal,
• utilizing said extracted synchronizing signal to clock data from said modified television signal,
• wherein the average power of said supplemental data signal matches the average power of the portion of the sideband removed in said removing step.

A method of transmitting digital data in a television channel without disturbing television transmission quality wherein said channel carries a composite television signal that includes audio, video and synchronizing information, said method comprising:

• modulating a carrier signal with representations of data from a digital data stream thereby to generate said supplemental data signal,
• generating upper and lower sidebands of said television signal wherein one of said sidebands includes a vestigial sideband of said television signal,
• removing a portion of said vestigial sideband and substituting therefor a representation of said supplemental data signal,
• deriving synchronizing information from a residual portion of at least one of said sideband,
• transmitting a modified television signal that includes a representation of said supplemental data signal, said residual synchronizing information, and said television signal,
• receiving said modified television signal at a receiver,
• extracting a synchronizing signal from a sideband of said modified television signal,
• utilizing said extracted synchronizing signal to clock data from said modified television signal,
• wherein the composite video signal includes a carrier and the supplemental data signal includes a carrier that is phase-shifted from the carrier of the composite video signal.

In combination with television signal transmission equipment operative to transmit a modified television signal that includes both video information and a digital data stream, the improvement comprising:

• a. an input for receiving a video signal from a video source,
• b. a mixer for converting said video signal to an intermediate frequency video signal having respective upper and lower sidebands,
• c. a first intermediate filter for bandpassing a first of the respective sidebands on a first side of a center frequency and for bandpassing at least a portion of a second of the respective sidebands for use in recovering synchronizing information,
• d. an input for receiving a digital data stream from a data source,
• e. a data modulator connected to said input for modulating a carrier with said digital data that is clocked in accordance with a clocking signal derived from synchronizing information of said video signal,
• f. a second mixer for converting the modulated digital data signal to an intermediate frequency data signal having respective upper and lower sidebands, said intermediate video and data signals being phase-shifted 90 degrees from each other by a phase shifter,
• g. a second intermediate filter for bandpassing one of said sidebands of said intermediate data signal on a second side of said center frequency of said second intermediate filter, and
• h. a combiner for combining the outputs of said first and second intermediate filters thereby to generate a modified television signal for transmission, wherein said first sideband carries representations of said video signal and said second sideband carries representations of said data signals.

In combination with television signal transmission equipment operative to transmit a modified television signal that includes a composite video signal including both video information and a digital data stream, the improvement comprising:

• a. an input for receiving a video signal from a video source,
• b. a mixer for converting said video signal to an intermediate frequency video signal having respective upper and lower sidebands,
• c. a first intermediate filter for bandpassing a first of the respective sidebands on a first side of a center frequency and for bandpassing at least a portion of a second of the respective sidebands for use in recovering synchronizing information,
• d. an input for receiving a digital data stream from a data source,
• e. a data modulator connected to said input for modulating a carrier with said digital data that is clocked in accordance with a clocking signal derived from synchronizing information of said video signal,
• f. a second mixer for converting the modulated digital data signal to an intermediate frequency data signal having respective upper and lower sidebands, said intermediate video and data signals being phase-shifted from each other by a phase shifter,
• g. a second intermediate filter for bandpassing one of said sidebands of said intermediate data signal on a second side of said center frequency of said second intermediate filter,
• h. a combiner for combining the outputs of said first and second intermediate filters thereby to generate a modified television signal for transmission, wherein said first sideband carries representations of said video signal and said second sideband carries representations of said data signals, and
• i. a reference generator for generating a reference clocking signal extracted from synchronizing information contained in said composite video signal, said reference clocking signal being used for generating a data clocking signal for clocking said digital data from said digital data source.

A client-server network system utilizing a conventional television channel for transferring digital data between a client and a server without disturbing video signal quality, said network system comprising:

• a mixer for converting a video signal to an intermediate frequency video signal having respective first and second sidebands,
• a first intermediate filter for bandpassing a first sideband of said video signal for use in recovering said video signal and for bandpassing a portion of said second sideband for use in recovering synchronizing information at a client-side receiver,
• a data modulator for modulating a carrier signal with a digital data clocked in accordance with a clocking signal derived from synchronizing information contained in said video signal,
• a second mixer for converting the modulated digital data signal to an intermediate frequency data signal having respective first and second sidebands, said intermediate video and data signals being phase-shifted 90 degrees from each other by a phase shifter,
• a second intermediate filter for bandpassing one of said sidebands of said intermediate data signal,
• a combiner for combining opposed sideband outputs of said first and second intermediate filters thereby to generate a modified television signal for transmission, wherein said first sideband carries representations of said video signal and second sideband carries representations of said data signals, and
• a receiver for generating a digital data stream from said modified television signal, said receiver including a circuit for regenerating a signal that carries digital data in a first portion of a vestigial sideband, for extracting synchronizing signals from a second portion of said vestigial sideband, for utilizing said extracted synchronizing signal to clock said digital data from said supplemental data signal, and for supplying said clocked digital data signals to said client.

A method of transmitting digital data in a television channel without disturbing television transmission quality wherein said channel carries a conventional television signal that includes audio, video and synchronizing information, said method comprising:

• modulating a carrier signal with representations of data from a digital data stream thereby to generate said supplemental data signal,
• generating upper and lower sidebands of said television signal wherein one of said sidebands includes a vestigial sideband of said television signal,
• removing a portion of said vestigial sideband and substituting therefore a representation of said supplemental data signal,
• deriving synchronizing information from a residual portion of at least one of said sideband,
• transmitting a modified television signal that includes a representation of said supplemental data signal, said residual synchronizing information, and said television signal,
• receiving said modified television signal at a receiver,
• extracting a synchronizing signal from a sideband of said modified television signal,
• utilizing said extracted synchronizing signal to clock data from said modified television signal,
• wherein, in said first extracting step, said synchronizing step is extracted from at least the 7th and higher harmonic of said television signal in order to retain sufficient usable quality of said synchronizing signal.

Television signal transmission equipment operative to transparently transmit digital data in a modified television signal without disturbing the quality of an original television signal, said equipment comprising:

• a mixer for converting said video signal to an intermediate frequency video signal having respective upper and lower sidebands,
• a first intermediate filter that bandpasses a first of said respective sidebands on a first side of a center frequency and that bandpasses at least a portion of a second of said respective sidebands for use in recovering synchronizing information,
• an input for receiving a digital data stream from a digital data source,
• a data modulator for modulating a carrier signal with said digital data that is clocked in accordance with a clocking signal derived from synchronizing information contained in said television signal,
• a second mixer for converting the modulated digital data signal to an intermediate frequency data signal having respective upper and lower sidebands, said intermediate video and data signals being phase-shifted 90 degrees from each other by a phase shifter,
• a second intermediate filter for bandpassing one of the sidebands of said intermediate frequency data signal on a second side of said center frequency of said second intermediate filter, and
• a combiner for combining the outputs of said first and second intermediate filters thereby to generate a modified television signal for transmission, wherein said first sideband carries representations of said video signal and second sideband carries representations of said synchronizing information and said data signals.