Digital television (HDTV) and analog television (NTSC) broadcast systems combined for simultaneous broadcast

摘要

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.