Demodulator for sampled chrominance signals including a Nyquist filter for recovering wideband I color difference signals

Claim 2

In a video signal processor including a source of I and Q chrominance samples, said I chrominance samples representing asymmetrical-sideband modulated I color difference signals wherein the frequency band of a first sideband is wider than a second sideband, and said Q chrominance samples representing double-sideband modulated Q color difference signals plus quadrature crosstalk components of said I color difference signals, apparatus comprising: separating means responsive to said chrominance samples for providing samples representative of said asymmetrical sideband modulated I signal and of the quadrature crosstalk I signal components of said Q samples to the substantial exclusion of the double-sideband modulated Q signal component of said Q chrominance samples; Nyquist filtering means coupled to said separating means for providing a vestigial sedeband modulated signal representing said I signal; and demodulating means coupled to said Nyquist filtering means for providing samples representative of said I signal and having a substantially uniform range of ampitude values over a frequency band substantially equal in width to said first I signal sideband.

Claim 3

The apparatus of claim 1 wherein the separating means comprises: demodulating means responsive to said chrominance samples for providing samples representative of said Q signal and having a frequency band substantially equivalent to the frequency band of the lower I signal sideband; low pass filtering means for limiting the frequency band of the samples provided by said demodulating means to the width of the upper Q signal sideband of said chrominance signal; modulating means coupled to said low pass filtering means for providing samples representative of the double-sideband modulated Q signal to the substantial exclusion of said I signal; means for subtracting the samples provided by said modulating means from said chrominance samples to produce samples representative of the asymmetrical-sideband modulated I signal component of said chrominance signal to the substantial exclusion of the double-sideband modulated Q signal component of said chrominance signal.

Claim 4

The apparatus of claim 1 wherein the separating means comprises: a bandpass filter coupled to said source having a frequency band substantially equal to that of said upper I and Q signal sidebands; decimating means coupled to said bandpass filter for replacing I chrominance samples by a reference value; means for subtracting the samples provided by said decimating means from the chrominance samples provided by said source to produce samples representative of the asymmetrical-sideband modulated I signal component of said chrominance signal to the substantial exclusion of the Q signal component of said Q signal sidebands.

Claim 5

In a digital color television receiver for processing digital chrominance samples representing a chrominance signal that includes a double-sideband suppressed-carrier modulated Q signal component, an asymmetrical-sideband suppressed-carrier modulated I signal component and an I signal component which produces quadrature distortion; apparatus comprising separating means for providing digital Q signal samples representative of the modulated Q signal component of the chrominance signal to the substantial exclusion of the modulated I signal component and of the quadrature distortion producing I signal component; subtraction means, coupled to said separating means, for subtracting said digital Q signal samples from said digital chrominance samples to produce digital samples representing a signal that includes said modulated I signal component and said quadrature distortion producing I signal component to the substantial exclusion of said modulated Q signal component; Nyquist filtering means coupled to said subtracting means for providing digital samples representing a vestigial sideband suppressed carrier modulated I signal; and demodulating means coupled to said Nyquist filtering means for providing digital samples representative of a demodulated I signal and having a substantially uniform range of amplitude values over a frequency band substantially equal in width to the wider sideband of said asymmetrically modulated I signal.

Claim 6

In a digital color television receiver for processing digital chrominance samples representing a chrominance signal that includes a double-sideband suppressed-carrier modulated Q signal component, an asymmetrical-sideband suppressed-carrier modulated I signal component and an I signal component which produces quadrature distortion; apparatus comprising separating means for providing digital Q signal samples representative of the modulated Q signal component of the chrominance signal to the substantial exclusion of the modulated I signal component and of the quadrature distortion producing I signal component; subtraction means, coupled to said separating means, for subtracting said digital Q signal samples from said digital chrominance samples to produce digital samples representing a signal that includes said modulated I signal component and said quadrature distortion producing I signal component to the substantial exclusion of said modulated Q signal component; Nyquist filtering means coupled to said subtracting means for providing digital samples representing a vestigial sideband suppressed carrier modulated I signal; and demodulating means coupled to said Nyquist filtering means for providing digital samples representative of a demodulated I signal and having a substantially uniform range of amplitude values over a frequency band substantially equal in width to the wider sideband of said asymmetrically modulated I signal.

Claim 7

The apparatus of claim 4 wherein said separating means comprises: demodulating means responsive to said chrominance samples for providing samples representative of a demodulated Q signal and having a frequency band substantially equivalent to the larger of the frequency bands of the sidebands of said modulated I signal; and low pass filtering means for limiting the frequency band of the samples provided by said demodulating means to the width of one sideband of the modulated Q signal component of said chrominance signal.

Claim 8

The apparatus of claim 4 wherein said separating means comprises: a bandpass filter for modifying said digital chrominance samples to have a frequency band substantially equal to the frequency band of one sideband of the modulated Q signal component of said chrominance signal; and decimating means coupled to said bandpass filter for replacing the components of said modified chrominance samples that represent said I signal by a reference value.

Claim 9

In a video signal processor including a source of chrominance samples having alternating I and Q samples, said I samples having components that represent standard I color difference signals and said Q samples having components that represent standard Q color difference signals and components that represent I color difference signal components that produce quadrature distortion, apparatus comprising: demodulating means coupled to said source for separating the Q samples from said chrominance samples;

Claim 10

In a video signal processor including a source of chrominance samples having alternating I and Q samples, said I samples having components that represent standard I color difference signals and said Q samples having components that represent standard Q color difference signals and components that represent I color difference signal components that produce quadrature distortion, apparatus comprising: demodulating means coupled to said source for separating the Q samples from said chrominance samples;

Claim 11

low pass filtering means coupled to said demodulating means for removing the quadrature distortion producing I color difference signal components from said Q samples; modulating means coupled to said low pass filtering means for providing modulated samples having alternating low pass filtered Q samples and samples of a reference value and being synchronized to the Q and I samples of said chrominance samples respectively; means coupled to said source and to said modulating means for subtracting said modulated samples from said chrominance samples to provide samples representing said I color difference signals and said quadrature distortion producing I color difference signals; and Nyquist filtering means coupled to said subtracting means for providing Nyquist filtered samples representing said I signal; demodulating means coupled to said Nyquist filtering means for providing samples representing said I signal and having a substantially uniform range of amplitude values over the frequency band of said I signals.

Claim 12

low pass filtering means coupled to said demodulating means for removing the quadrature distortion producing I color difference signal components from said Q samples; modulating means coupled to said low pass filtering means for providing modulated samples having alternating low pass filtered Q samples and samples of a reference value and being synchronized to the Q and I samples of said chrominance samples respectively; means coupled to said source and to said modulating means for subtracting said modulated samples from said chrominance samples to provide samples representing said I color difference signals and said quadrature distortion producing I color difference signals; and Nyquist filtering means coupled to said subtracting means for providing Nyquist filtered samples representing said I signal; demodulating means coupled to said Nyquist filtering means for providing samples representing said I signal and having a substantially uniform range of amplitude values over the frequency band of said I signals.

Claim 13

In a video signal processor including a source of chrominance samples having alternating I and Q samples said Q samples having components that represent standard Q color difference signals and components that represent quadrature distortion producing I color difference signals, apparatus comprising: bandpass filtering means for reducing the frequency band of said chrominance samples to remove components of the Q samples that represent the quadrature distortion producing I color difference signals; decimating means coupled to said bandpass filtering means for substituting samples of a reference value for the I signal samples provided by said filtering means; means for subtracting the samples provided by said decimating means from said chrominance samples to provide samples representing said I color difference signals and said quadrature distortion producing I color difference signals; and Nyquist filtering means coupled to said subtracting means for providing vestigial sideband filtered samples representing said I signal; demodulating means coupled to said Nyquist filter for providing samples representing said I signal and having a substantially uniform range of amplitude values over the frequency band of said I signals.

Claim 14

In a video signal processor including a source of chrominance samples having alternating I and Q samples said Q samples having components that represent standard Q color difference signals and components that represent quadrature distortion producing I color difference signals, apparatus comprising: bandpass filtering means for reducing the frequency band of said chrominance samples to remove components of the Q samples that represent the quadrature distortion producing I color difference signals; decimating means coupled to said bandpass filtering means for substituting samples of a reference value for the I signal samples provided by said filtering means; means for subtracting the samples provided by said decimating means from said chrominance samples to provide samples representing said I color difference signals and said quadrature distortion producing I color difference signals; and Nyquist filtering means coupled to said subtracting means for providing vestigial sideband filtered samples representing said I signal; demodulating means coupled to said Nyquist filter for providing samples representing said I signal and having a substantially uniform range of amplitude values over the frequency band of said I signals.