Apparatus for NTSC signal interference cancellation through the use of digital recursive notch filters
First Claim
1. A system for removing NTSC components, the NTSC components including the picture carrier, chrominance subcarrier, and audio carrier components, of a received television signal including a high definition television (HDTV) signal, comprising:
- an adder having a plurality of inputs and an output, a first input of said adder being adapted for coupling to a tuner for receiving said received television signals;
a first bi-quadratic recursive digital filter having an input adapted for coupling to said tuner for receiving said received television signals from said tuner, said first filter having an adjustable notch at the carrier frequency of the NTSC picture carrier component of said received television signals for isolating said NTSC picture carrier component, whereby said filter independently adjusts the center frequency and gain of said adjustable notch to match both the frequency and amplitude of said NTSC picture carrier component, said first filter producing a phase shift of zero at said center frequency of said first filter'"'"'s notch to provide a first filtered signal output, the first filtered signal output coupled to a second input of said adder;
a second bi-quadratic recursive digital filter having an input adapted for coupling to said tuner for receiving said received television signals from said tuner, and second filter having an adjustable notch at the subcarrier frequency of the NTSC chrominance component of said received television signals for isolating said NTSC chrominance component, whereby said filter independently adjusts the center frequency and gain of said adjustable notch to match both the frequency and amplitude of said NTSC chrominance component, said second filter producing a phase shift of zero at said center frequency of said second filter'"'"'s notch to provide a second filtered signal output, the second filtered signal output coupled to a third input of said adder; and
a third bi-quadratic recursive digital filter having an input adapted for coupling to said tuner for receiving said received television signals from said tuner, said third filter having an adjustable notch at the carrier frequency of the NTSC audio component of said received television signals for isolating said NTSC audio component, whereby said filter independently adjusts the center frequency and gain of said adjustable notch to match both the frequency and amplitude of said NTSC audio component, said third filter producing a phase shift of zero at said center frequency of said third filter'"'"'s notch to provide a third filtered signal output, the third filtered signal output coupled to a fourth input of said adder;
said adder operating to subtract said first, second, and third filtered signal outputs applied to said second, third, and fourth adder inputs from said received signal input thereby removing said isolated NTSC picture carrier, chrominance, and audio components from said received television signals producing the signal output of said adder.
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Accused Products
Abstract
An NTSC interference canceler for eliminating NTSC signal interference from a HDTV signal uses recursive notch filters with independently adjustable gains and center frequencies to isolate an NTSC signal'"'"'s major components, i.e. the picture carrier signal, the chrominance subcarrier signal and the audio carrier signal. A single filter is used to isolate each NTSC interference signal component, with each particular filter'"'"'s gain and center frequency being independently adjusted to match the amplitude and frequency of the particular NTSC interference signal component to be isolated by the filter. Once isolated, these interference signal components are substracted from the received television signal which includes both the NTSC interference signal and the HDTV signal. In this manner, the NTSC interference is removed from the HDTV signal.
403 Citations
51 Claims
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1. A system for removing NTSC components, the NTSC components including the picture carrier, chrominance subcarrier, and audio carrier components, of a received television signal including a high definition television (HDTV) signal, comprising:
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an adder having a plurality of inputs and an output, a first input of said adder being adapted for coupling to a tuner for receiving said received television signals; a first bi-quadratic recursive digital filter having an input adapted for coupling to said tuner for receiving said received television signals from said tuner, said first filter having an adjustable notch at the carrier frequency of the NTSC picture carrier component of said received television signals for isolating said NTSC picture carrier component, whereby said filter independently adjusts the center frequency and gain of said adjustable notch to match both the frequency and amplitude of said NTSC picture carrier component, said first filter producing a phase shift of zero at said center frequency of said first filter'"'"'s notch to provide a first filtered signal output, the first filtered signal output coupled to a second input of said adder; a second bi-quadratic recursive digital filter having an input adapted for coupling to said tuner for receiving said received television signals from said tuner, and second filter having an adjustable notch at the subcarrier frequency of the NTSC chrominance component of said received television signals for isolating said NTSC chrominance component, whereby said filter independently adjusts the center frequency and gain of said adjustable notch to match both the frequency and amplitude of said NTSC chrominance component, said second filter producing a phase shift of zero at said center frequency of said second filter'"'"'s notch to provide a second filtered signal output, the second filtered signal output coupled to a third input of said adder; and a third bi-quadratic recursive digital filter having an input adapted for coupling to said tuner for receiving said received television signals from said tuner, said third filter having an adjustable notch at the carrier frequency of the NTSC audio component of said received television signals for isolating said NTSC audio component, whereby said filter independently adjusts the center frequency and gain of said adjustable notch to match both the frequency and amplitude of said NTSC audio component, said third filter producing a phase shift of zero at said center frequency of said third filter'"'"'s notch to provide a third filtered signal output, the third filtered signal output coupled to a fourth input of said adder; said adder operating to subtract said first, second, and third filtered signal outputs applied to said second, third, and fourth adder inputs from said received signal input thereby removing said isolated NTSC picture carrier, chrominance, and audio components from said received television signals producing the signal output of said adder. - View Dependent Claims (2, 3, 4, 5, 6, 7, 8, 9, 10, 11, 12, 13, 14, 15, 16, 17, 18, 19)
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20. A filter for removing an NTSC component of a received television signal including a high definition television (HDTV) signal, comprising:
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a bi-quadratic recursive digital notch filter having an adjustable notch at the carrier frequency of said NTSC component of said received television signal for isolating said NTSC component, whereby said bi-quadratic recursive digital notch filter independently adjusts the center frequency and gain of said adjustable notch to match both the frequency and amplitude of said NTSC component, said bi-quadratic recursive digital notch filter producing a phase shift of approximately zero at said center frequency of said bi-quadratic recursive digital notch filter'"'"'s notch; and a summing circuit, coupled to said bi-quadratic recursive digital notch filter and to said received television signals, to subtract said isolated NTSC component from said received television signals. - View Dependent Claims (21, 22, 23, 24, 25, 26, 27)
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28. A television receiver for removing NTSC components, including an NTSC picture carrier component, an NTSC chrominance subcarrier component, and an NTSC audio carrier component, from a received television signal including a high definition television (HDTV) signal and for processing said high definition television signal for display, comprising:
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a tuner including means for receiving television signals and band-limiting said received television signals, a first bi-quadratic recursive digital filter, coupled to said tuner, having an adjustable notch at the carrier frequency of the NTSC picture carrier component of said received, band-limited television signals for isolating said NTSC picture carrier component, whereby said first bi-quadratic recursive digital filter independently adjusts the center frequency and gain of said adjustable notch to match both the frequency and amplitude of said NTSC picture carrier component, said first filter producing a phase shift of zero at said center frequency of said first filter'"'"'s notch; a second bi-quadratic recursive digital filter, coupled to said tuner, having an adjustable notch at the subcarrier frequency of the NTSC chrominance component of said received, band-limited television signals for isolating said NTSC chrominance component, whereby said second bi-quadratic recursive digital filter independently adjusts the center frequency and gain of said adjustable notch to match both the frequency and amplitude of said NTSC chrominance component, said second bi-quadratic recursive digital filter producing a phase shift of zero at said center frequency of said second filter'"'"'s notch; a third bi-quadratic recursive digital filter, coupled to said tuner, having an adjustable notch at the carrier frequency of the NTSC audio component of said received, band-limited television signals for isolating said NTSC audio component, whereby said third bi-quadratic recursive digital filter independently adjusts the center frequency and gain of said adjustable notch to match both the frequency and amplitude of said NTSC audio component, said third bi-quadratic recursive digital filter producing a phase shift of zero at said center frequency of said third bi-quadratic recursive digital filter'"'"'s notch; a summing circuit, coupled to said first, second, and third bi-quadratic recursive digital filters and to said tuner, to subtract said isolated NTSC picture carrier, chrominance subcarrier, and audio carrier components from said received, band-limited television signals and to output said high definition television components, and a demodulator, coupled to the output of said summing circuit, to demodulate said high definition television components for display thereof. - View Dependent Claims (29, 30, 31, 32, 33, 34, 35, 36, 37, 38, 39, 40, 41, 42, 43, 44, 45)
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46. A television receiver for removing an NTSC component of a received television signal including a high definition television (HDTV) signal and for processing said high definition television signal for display, comprising:
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a tuner including means for receiving television signals and band-limiting said received television signals, a recursive digital notch filter, coupled to said tuner, having an adjustable notch at the carrier frequency of said NTSC component of said received, band-limited television signals for isolating said NTSC component, said filter producing a phase shift of zero at said center frequency of said filter'"'"'s notch, whereby said recursive digital notch filter independently adjusts the center frequency of said adjustable notch to match the frequency of said NTSC component; a summing circuit, coupled to said recursive digital notch filter and to said tuner, to subtract said isolated NTSC component from said received, band-limited television signals and to output said high definition television components, and a demodulator, coupled to said summing circuit, to demodulate said high definition television components for display thereof. - View Dependent Claims (47, 48, 49, 50)
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51. A filter for removing NTSC interference from a television signal, the filter comprising:
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an adjustable gain recursive digital notch filter having a notch centered at the carrier frequency of a preselected NTSC signal component of the television signal and adapted for coupling to a tuner for receiving the television signal, for isolating the preselected NTSC signal component from the received television signal and for outputting the isolated NTSC signal component; means for adjusting the gain of the recursive digital filter as a function of the power of the preselected NTSC signal component to a level whereat the amplitude of the isolated NTSC signal component output by the adjustable gain recursive digital notch filter approximates the amplitude of the preselected NTSC signal component; and a summing circuit adapted for coupling to the tuner and coupled to the recursive digital notch filter for receiving the isolated NTSC signal component and for subtracting the isolated NTSC signal component from the television signal.
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Specification