Patent ID: 6184921
Filing Date: 2001-02-06
Classification: H04L,H04N

Abstract:
A method of transmitting a digital television signal through a channel subject at times to the presence of a co-channel NTSC analog television signal having a modulated video carrier, a modulated color subcarrier, and a modulated audio carrier, said method comprising steps of:providing an N-level digitally encoded signal at a symbol rate f.sub.s substantially equal to three times the NTSC color subcarrier frequency, N being a plural integer;generating a carrier signal having a nominal frequency offset below the co-channel NTSC audio carrier frequency by a frequency corresponding to a NTSC horizontal scanning rate;modulating the amplitude of said carrier signal with said N-level digitally encoded signal to generate first and second amplitude-modulation sidebands; andforming a transmission signal in response to said amplitude-modulation sidebands.