VSB HDTV transmission system with reduced NTSC co-channel interference

A method of transmitting a television signal over a television channel comprising:

• providing an N-level digitally encoded signal at a sample rate fs substantially equal to three times the NTSC color subcarrier frequency;
• generating a carrier signal having a frequency less than the frequency of the picture carrier of an NTSC co-channel signal by an amount of about fs/12;
• and
• modulating said carrier signal with said N-level digitally encoded signal for forming a transmission signal comprising a suppressed carrier, VSB signal having respective Nyquist slopes at the lower and upper edges of said channel, the center frequency of the Nyquist slope at the lower edge of said channel being substantially coincident with the frequency of said carrier signal.

A television signal receiver comprising:

• means for receiving an N-level digitally encoded signal modulating a suppressed carrier signal, said N-level signal having a sample rate fs substantially equal to three times the NTSC color subcarrier frequency and said suppressed carrier signal having a frequency less than the frequency of the picture carrier of an NTSC co-channel signal by an amount of about fs/12;
• means for demodulating said received N-level signal;
• filter means processing said demodulated signal for providing an M-level output signal, where M is greater than N, said filter means having a frequency response including a notch at a frequency substantially equal to fs/12;
• and
• means for converting said M-level signal to an N-level signal representing a televised image.

A television signal receiver comprising:

• means for receiving an N-level digitally encoded signal modulating a suppressed carrier signal, said N-level signal having a sample rate fs substantially equal to three time the NTSC color subcarrier frequency and said suppressed carrier signal having a frequency less than the frequency of the picture carrier of an NTSC co-channel signal by an amount of about fs/12;
• means for demodulating said received N-level signal;
• filter means comprising means for delaying said demodulated signal by an interval substantially equal to 12/fs and means for subtracting the delayed signal from said demodulated signal for providing an M-level output signal, where M is greater than N;
• and
• means for converting said M-level signal to an N-level signal representing a televised image.

A receiver for receiving a television signal transmitted over a selected channel comprising:

• means for receiving a transmission signal comprising a suppressed carrier, VSB signal having respective Nyquist slopes at the lower and upper edges of said selected channel, the center frequency of the Nyquist slope at the lower edge of said selected channel being substantially coincident with the frequency of said suppressed carrier, said suppressed carrier being modulated by an N-level digitally encoded signal having a sample rate fs substantially equal to three times the NTSC color subcarrier frequency and said suppressed carrier having a frequency less than the frequency of the picture carrier of an NTSC co-channel signal by an amount of about fs/12;
• means coupled to said receiving means for demodulating said N-level signal;
• and
• filter means processing said demodulated signal for providing an N-level output signal, said filter means having a frequency response including notches at frequencies substantially equal to fs/12 and 5fs/12.

A receiver for receiving a television signal transmitted over a selected channel comprising:

• means for receiving a transmission signal comprising a suppressed carrier, VSB signal having respective Nyquist slopes at the lower and upper edges of said selected channel, the center frequency of the Nyquist slope at the lower edge of said selected channel being substantially coincident with the frequency of said suppressed carrier, and a pilot signal, said suppressed carrier being modulated by an N-level digitally encoded signal having a sample rate fs substantially equal to three times the NTSC color subcarrier frequency and said suppressed carrier having a frequency less than the frequency of the picture carrier of an NTSC co-channel signal by an amount equal to about fs/12;
• means responsive to said pilot signal for developing a regenerated carrier signal having frequency and phase characteristics corresponding to said suppressed carrier signal;
• means coupled to said receiving means and responsive to said regenerated carrier signal for demodulating said N-level signal;
• and
• filter means processing said demodulated signal for providing an N-level output signal, said filter means having a frequency response including notches at frequencies substantially equal to fs/12 and 5fs/12.

A method of transmitting and receiving a television signal over a selected channel comprising:

• providing a transmission signal comprising a suppressed carrier, VSB signal having respective Nyquist slopes at the upper and lower edges of said selected channel, the center frequency of the Nyquist slope at the lower edge of said selected channel being substantially coincident with the frequency of said suppressed carrier, said suppressed carrier being modulated by an N-level digitally encoded signal having a sample rate fs substantially equal to three times the NTSC color subcarrier frequency and said suppressed carrier having a frequency less than the frequency of the picture carrier of an NTSC co-channel signal by an amount equal to about fs/12;
• transmitting said transmission signal over said selected channel;
• receiving said transmitted signal;
• demodulating said received signal for recovering said N-level signal;
• subjecting said recovered N-level signal to a filter response having notches at frequencies substantially equal to fs/12 and 5fs/12 for providing a filtered M-level signal, where M is greater than N;
• and
• converting said M-level signal to an N-level output signal representing said television signal.

A method of transmitting and receiving a television signal over a selected channel comprising:

• providing a transmission signal comprising a suppressed carrier, VSB signal having respective Nyquist slopes at the upper and lower edges of said selected channel, the center frequency of the Nyquist slope at the lower edge of said selected channel being substantially coincident with the frequency of said suppressed carrier, and a pilot signal, said suppressed carrier being modulated by an N-level digitally encoded signal having a sample rate fs substantially equal to three times the NTSC color subcarrier frequency and said suppressed carrier having a frequency less than the frequency of the picture carrier of an NTSC co-channel signal by an amount equal to about fs/12;
• transmitting said transmission signal over said selected channel;
• receiving said transmitted signal;
• regenerating a carrier signal in response to said received pilot signal, said regenerated carrier signal having frequency and phase characteristics corresponding to said suppressed carrier;
• demodulating said received signal in response to said regenerated carrier signal for recovering said N-level signal;
• subjecting said recovered N-level signal to a filter response having notches at frequencies substantially equal to fs/12 and 5fs/12 for providing a filtered M-level signal, where M is greater than N;
• and
• converting said M-level signal to an N-level output signal representing said television signal.