Patent ID: 6057877
Filing Date: 2000-05-02
Classification: H04L,H04N

Abstract:
A digital television signal receiver for digital television signals that are received as vestigial-sideband amplitude-modulation of a carrier and that are apt to be accompanied at times by co-channel interfering analog television signals of undesirable strengths, said digital television signal receiver including:amplifier circuitry for supplying an amplified vestigial-sideband amplitude-modulated digital television signal;demodulation circuitry responsive to said amplified vestigial-sideband amplitude-modulated digital television signal for supplying at least one baseband signal;symbol decoding apparatus for symbol decoding an I-channel baseband signal to generate symbol decoding results, said symbol decoding apparatus connected to receive said I-channel baseband signal as an input signal from said demodulation circuitry, said symbol decoding apparatus includinga selectively operable filter for suppressing any artifacts of a co-channel interfering analog television signal accompanying said I-channel baseband signal to be symbol decoded, said filter being operable when and only when said symbol decoding apparatus receives a signal indicating there is a significant amount of co-channel NTSC interference;error correction circuitry for correcting errors in symbol decoding results from said symbol decoding apparatus;a co-channel interference detector connected to receive a further baseband input signal from said demodulation circuitry, said co-channel interference detector being of a type insensitive to the direct term of the system function of baseband signal it receives as its input signal and comprising:a first comb filter combining said further baseband input signal with itself as subjected to a first amount of differential delay to generate a first comb filter response, in which artifacts arising from synchronous detection of said co-channel interfering analog television signal are suppressed, and;a second comb filter combining said further baseband input signal with itself as subjected to a second amount of differential delay to generate a second comb filter response, in which the artifacts arising from synchronous detection of said co-channel interfering analog television signal are reinforced, and in which the direct term of system characteristic arising from synchronous detection of said carrier is similar to that in said first comb filter response;a first amplitude detector for detecting the amplitude of said first comb filter response to generate a first amplitude detection response;a second amplitude detector for detecting the amplitude of said second comb filter response to generate a second amplitude detection response; andan amplitude comparator for comparing said first and second amplitude detection responses and, when and only when said first and second amplitude detection responses differ by more than a prescribed amount, supplying said signal indicating there is said significant amount of co-channel NTSC interference.