Apparatus for generating timing signals for a digital television signal receiver
First Claim
1. Apparatus for generating timing signals from digital television signals, comprising:
- a filter/complement for filtering said digital television signals having a first output terminal producing a low-pass filtered signal, and a second output terminal producing a high-pass filtered signal complementary to the low-pass filtered signal; and
a sample clock generating circuit, coupled to the second output terminal of the filter/complement, for producing a sample clock signal responsive to the high-pass filtered signal;
whereinthe sample clock generating circuit is a band edge timing recovery circuit; and
the high-pass filtered signal is a complex signal which contains a positive frequency component and a negative frequency component, and the sample clock generating circuit comprises;
a first band edge filter, coupled to the filter/complement, for extracting the positive frequency component from the high-pass filtered signal;
a second band edge filter, coupled to the filter/complement, for extracting the negative frequency component from the high-pass filtered signal;
a complex conjugating circuit coupled to one of the first and second filters;
a multiplier having a first input terminal coupled to the other one of the first and second filters, and a second input terminal coupled to the complex conjugating circuit; and
a serial connection of a phase detector, loop filter and voltage controlled oscillator coupled to the multiplier and producing the sample clock signal.
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Accused Products
Abstract
A QAM/VSB digital receiver is disclosed which includes a source of a QAM/VSB signal. An analog-to-digital converter is coupled to the QAM/VSB signal source, and is further responsive to a sample clock signal. A filter/complement is coupled to the analog-to-digital converter and has a first output terminal which produces a low-pass filtered QAM/VSB signal, and a second output terminal which produces a high-pass filtered QAM/VSB signal complementary to the low-pass filtered QAM/VSB signal. A sample clock generating circuit is coupled to the second output terminal of the filter/complement and produces the sample clock signal in response to the high-pass filtered QAM/VSB signal.
136 Citations
21 Claims
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1. Apparatus for generating timing signals from digital television signals, comprising:
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a filter/complement for filtering said digital television signals having a first output terminal producing a low-pass filtered signal, and a second output terminal producing a high-pass filtered signal complementary to the low-pass filtered signal; and a sample clock generating circuit, coupled to the second output terminal of the filter/complement, for producing a sample clock signal responsive to the high-pass filtered signal;
whereinthe sample clock generating circuit is a band edge timing recovery circuit; and the high-pass filtered signal is a complex signal which contains a positive frequency component and a negative frequency component, and the sample clock generating circuit comprises; a first band edge filter, coupled to the filter/complement, for extracting the positive frequency component from the high-pass filtered signal; a second band edge filter, coupled to the filter/complement, for extracting the negative frequency component from the high-pass filtered signal; a complex conjugating circuit coupled to one of the first and second filters; a multiplier having a first input terminal coupled to the other one of the first and second filters, and a second input terminal coupled to the complex conjugating circuit; and a serial connection of a phase detector, loop filter and voltage controlled oscillator coupled to the multiplier and producing the sample clock signal. - View Dependent Claims (2, 3, 4, 5)
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6. Apparatus for generating timing signals from digital television signals, comprising:
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a filter/complement for filtering said digital television signals having a first output terminal producing a low-pass filtered signal, and a second output terminal producing a high-pass filtered signal complementary to the low-pass filtered signal; and a sample clock generating circuit, coupled to the second output terminal of the filter/complement, for producing a sample clock signal responsive to the high-pass filtered signal said sample clock generating circuit comprising a band edge timing recovery circuit; wherein the high-pass filtered signal is a simple real signal which contains a positive frequency component and a negative frequency component, and the sample clock generating circuit comprises; a first band edge filter, coupled to the filter/complement, for extracting one of the positive and negative frequency components from the high-pass filtered signal; a complex conjugating circuit, coupled to the filter/complement; a second band edge filter, coupled to the complex conjugating circuit, for extracting the other one of the positive and negative frequency components from the high-pass filtered signal; a first phase detector, coupled to the first band edge filter; a second phase detector, coupled to the second band edge filter; a subtractor, having a minuend input terminal coupled to the first phase detector, and a subtrahend input terminal coupled to the second phase detector; and a series connection of a loop filter and a voltage controlled oscillator coupled to a signal combiner and producing the sample clock signal. - View Dependent Claims (7, 8, 9, 10)
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11. Apparatus for generating timing signals from digital television signals, comprising:
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a filter/complement for filtering said digital television signals having a first output terminal producing a low-pass filtered signal, and a second output terminal producing a high-pass filtered signal complementary to the low-pass filtered signal; and a sample clock generating circuit, coupled to the second output terminal of the filter/complement, for producing a sample clock signal responsive to the high-pass filtered signal, said sample clock generating circuit comprising a band edge timing recovery circuit;
wherein;the second output terminal of the filter/complement comprises a real component signal output terminal and an imaginary component signal output terminal, and the high-pass filtered signal contains a positive frequency component and a negative frequency component; and the sample clock generating circuit comprises; a first band edge filter, having a real signal input terminal coupled to the real signal output terminal of the filter/complement, and an imaginary signal input terminal, for extracting one of the positive and negative frequency components from the high-pass filtered signal; a first multiplexer, having a first data input terminal coupled to the imaginary component signal output terminal of the filter/complement, a second data input terminal coupled to a source of a zero-valued signal, an output terminal coupled to the imaginary signal input terminal of the first band edge filter, and a control input terminal; a controllable I/Q swapper circuit, having respective real and imaginary signal input terminals coupled to corresponding output terminals of the filter/complement, respective real and imaginary signal output terminals, and a control input terminal; a second band edge filter, having a real signal input terminal coupled to the real signal output terminal of the controllable I/Q swapper circuit, and an imaginary signal input terminal, for extracting the other one of the positive and negative frequency components from the high-pass filtered signal; a second multiplexer, having a first data input terminal coupled to the imaginary signal output terminal of the controllable I/Q swapper circuit, a second data input terminal coupled to the source of a zero-valued signal, an output terminal coupled to the imaginary signal input terminal of the second band edge filter, and a control input terminal; a complex conjugating circuit, coupled to the second band edge filter; a complex multiplier, having a first input terminal coupled to the first band edge filter, and a second input terminal coupled to the complex conjugating circuit; a complex multiplexer, having a first input terminal coupled to the first band edge filter, a second input terminal coupled to the complex multiplier, and a control input terminal; a first phase detector, coupled to the complex multiplexer; a second phase detector, coupled to the second band edge filter; a third multiplexer, having a first data input terminal coupled to the second phase detector, a second data input terminal coupled to the source of a zero-valued signal, and a control input terminal; a subtractor, having a minuend input terminal coupled to the first phase detector, and a subtrahend input terminal coupled to the third multiplexer; a series connection of a loop filter and a voltage controlled oscillator coupled to a signal combiner and producing the sample clock signal; and a source of control signal having one of a first and second state, coupled to respective control input terminals of the controllable I/Q swapper circuit, the first, second and third multiplexers, and the complex multiplexer;
wherein;when the control signal is in the first state; the first multiplexer is conditioned to couple the signal from the filter/complement to the first band edge filter; the controllable I/Q swapper circuit is conditioned to pass the signal from the filter/complement to its respective output terminals unchanged; the second multiplexer is conditioned to couple the signal from the controllable I/Q swapper circuit to the second band edge filter; the complex multiplexer is conditioned to couple the signal from the complex multiplier to the first phase detector; and the third multiplexer is conditioned to couple the signal from the zero-valued signal source to the subtractor; and when the control signal is in the second state; the first multiplexer is conditioned to couple the signal from the zero-valued signal source to the first band edge filter; the controllable I/Q swapper circuit is conditioned to pass swapped I/Q data signals from the filter/complement to its respective output terminals; the second multiplexer is conditioned to couple the signal from the zero-valued signal source to the second band edge filter; the complex multiplexer is conditioned to couple the signal from the first band edge filter to the first phase detector; and the third multiplexer is conditioned to couple the signal from the second phase detector to the subtractor. - View Dependent Claims (12, 13, 14)
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15. In a receiver for television signals, apparatus for sampling said television signals comprising:
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an analog-to-digital (A/D) converter for periodically sampling said television signals in response to a timing signal to produce sampled television signals; a quadrature demodulator, coupled to said A/D converter, for demodulating said sampled television signals into an in-phase component and a quadrature component; a first matched filter/complement, coupled to said quadrature demodulator, for filtering said in-phase component having a first output terminal producing an in-phase low pass filtered signal, and a second output terminal having an in-phase high pass filtered signal complementary to the in-phase low pass filtered signal; a second matched filter/complement, coupled to said quadrature demodulator, for filtering said quadrature component having a first output terminal producing a quadrature low pass filtered signal, and a second output terminal having a quadrature high pass filtered signal complementary to the quadrature low pass filtered signal; and a timing signal generating circuit, coupled to the second output terminals of the first and second filter/complements, for producing the timing signal for said A/D converter. - View Dependent Claims (16, 17, 18, 19, 20, 21)
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Specification