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Digital television (HDTV) and analog television (NTSC) broadcast systems combined for simultaneous broadcast
| Details |
Inventors: Vaughan, Thomas J.;
Assignee:
Primary Examiner: Lee; Benny T.
Assistant Examiner:
Attorney, Agent or Firm: Dunn, Esq.; Robert T.
An HDTV broadcast transmission system and an analog NTSC broadcast transmission system are carried on the same tower and broadcast to the same area by adaptation of both systems: the NTSC system including: (a) a source of analog NTSC video signals, (b) an NTSC analog video signal exciter producing NTSC IF modulated analog video signals, (c) an NTSC frequency up converter and power amplifier producing NTSC RF modulated analog video signals (NTSC RF signals), (d) an NTSC broadcast antenna and (e) an all band VHF and UHF signal transmission line having an input end and an output end; the HDTV system including: (1) a source of digital video signals, (2) a digital video signal encoder producing IF modulated digital video signals and (3) a frequency up converter and power amplifier producing RF modulated digital video signals (HDTV RF signals) and an HDTV broadcast antenna; by combining the HDTV RF signals and NTSC RF signals at the input end of the transmission line and separating them at the output end and feeding them to the NTSC antenna and the HDTV antenna, respectively. In a preferred embodiment, the HDTV antenna is supported on the tower below the NTSC antenna and the antennas radiation patterns cover substantially overlapping broadcast reception areas around the tower. |
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DETAILED DESCRIPTION As stated above, the present invention has application to many broadcast systems where two channels of substantially different RF signals are broadcast from different antennas, fed by a common transmission line.
Particular embodiments described herein disclose method and means of providing the new HDTV broadcast transmission system in compliance with FCC guide lines and regulations and the other considerations described herein for the existing full service and LPTV broadcast NTSC stations; and these efforts follow one or more of the following guide lines: The station should use its present NTSC tower, or other support, for HDTV; The present top mounted NTSC antenna should stay.
The new HDTV transmitter power level will be 10% to 30% as great as the present NTSC transmitter power level; The HDTV transmission system must be an "Integrated" system, that is: it should include the HDTV transmitter, filter, transmission line and antenna as a total HDTV system integrated on the tower with the existing total NTSC system.
Clearly, it is not obvious how to achieve these guide lines and add an HDTV channel broadcast system, where the RF signals is in the Ultra High Frequency Band (UHF), to an existing NTSC channel broadcast system, particularly where the RF for NTSC Channels 2 to 13 is in the Very High Frequency Band (VHF), using a common transmission line, (preferably the existing NTSC transmission line) and the existing NTSC transmitter and broadcast antenna.
It is a general object of the present invention to provide a transmission system for two broadcast channels on the same tower using a common transmission line and different broadcast antennas.
It is a particular object to provide an HDTV transmission system for an existing NTSC tower that carries an operating NTSC transmission system.
It is another object of the present inventions to provide an HDTV broadcast system at a typical broadcast NTSC station that complies with all of the above and can be implemented with only minor revisions to the existing station NTSC system
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Television 
