Signal processing system
First Claim
1. A signal processing apparatus for processing signals that are sampled by a sampler operative at a sampling rate, the signals having a period corresponding to a received symbol rate, the apparatus comprising:
- a clock, operative at said sampling rate;
a numerically controlled oscillator operative at periods T;
an interpolator receiving samples at said sampling rate; and
a loop filter, coupled to said interpolator and said numerically controlled oscillator and having an output responsive to a difference between said periods T and said period corresponding to said received symbol rate of said sampled signals;
wherein said numerically controlled oscillator is responsive to said output of said loop filter and generates a first output signal that is representative of an interpolation distance between succeeding samples, and said interpolator interpolates said received samples according to said interpolation distance, and produces an output signal representative of interpolated samples, and said numerically controlled oscillator generates said first output signal whenever a state Ω
exceeds a division of said symbol period, and said interpolator generates said output signal representative of interpolated samples in response to said first output signal, wherein Ω
is a state representative of a number of elapsed operative periods of said numerically controlled oscillator.
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Abstract
A CMOS integrated signal processing system for a sampling receiver includes a timing recovery circuit, wherein an on-chip numerically controlled oscillator is operative at periods T that are initially equal to the nominal baud rate of the signals controls a sinc interpolator receiving samples at the sampling rate. A loop filter is coupled to the sinc interpolator and to the numerically controlled oscillator. The arrangement is capable of handling various symbol rates. The system includes a circuit for carrier recovery having a second on-chip numerically controlled oscillator, a digital derotation circuit responsive to the second numerically controlled oscillator, accepting an in phase component and a quadrature component of the sampled signals. An adaptive phase error estimation circuit is coupled in a feedback loop.
72 Citations
31 Claims
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1. A signal processing apparatus for processing signals that are sampled by a sampler operative at a sampling rate, the signals having a period corresponding to a received symbol rate, the apparatus comprising:
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a clock, operative at said sampling rate; a numerically controlled oscillator operative at periods T;
an interpolator receiving samples at said sampling rate; anda loop filter, coupled to said interpolator and said numerically controlled oscillator and having an output responsive to a difference between said periods T and said period corresponding to said received symbol rate of said sampled signals; wherein said numerically controlled oscillator is responsive to said output of said loop filter and generates a first output signal that is representative of an interpolation distance between succeeding samples, and said interpolator interpolates said received samples according to said interpolation distance, and produces an output signal representative of interpolated samples, and said numerically controlled oscillator generates said first output signal whenever a state Ω
exceeds a division of said symbol period, and said interpolator generates said output signal representative of interpolated samples in response to said first output signal, wherein Ω
is a state representative of a number of elapsed operative periods of said numerically controlled oscillator. - View Dependent Claims (2, 3, 4, 5, 6, 7, 8, 9, 10, 11, 12, 13, 14, 15)
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16. A signal processing apparatus for processing an input signal having a period corresponding to a received symbol rate, the apparatus comprising:
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a clock, operative at said sampling rate; a numerically controlled oscillator operative at periods T; a sinc interpolator receiving samples at said sampling rate;
wherein said interpolator comprises a finite impulse response filter operable according to a bank of coefficients, and an addressable memory having said coefficients memorized therein;a loop filter, coupled to said sinc interpolator and said numerically controlled oscillator and having an output responsive to a difference between said periods T and said period corresponding to said received symbol rate of said sampled signals; a sampler, comprising first and second analog-to-digital converters respectively coupled to an in phase component and a quadrature component of said signals;
wherein said sinc interpolator and said loop filter accept in phase and quadrature outputs of said sampler;wherein said numerically controlled oscillator is responsive to said loop filter and generates an output signal that is representative of an interpolation distance between succeeding samples, and said interpolator interpolates said received samples according to said interpolation distance, and produces an output signal representative of said interpolated samples; and
said numerically controlled oscillator, said sinc interpolator, and said loop filter comprise an integrated semiconductor circuit, wherein said output of said numerically controlled oscillator comprises a first output signal that is generated whenever said state Ω
exceeds a division of said symbol period, and said interpolator generates an output in response to said first output signal, wherein Ω
is a state representative of a number of elapsed operative periods of said numerically controlled oscillator. - View Dependent Claims (17, 18, 19, 20, 21, 22, 23, 24)
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25. A signal processing apparatus for processing signals that are sampled by a sampler operative at a sampling rate, the signals having a period corresponding to a received symbol rate, the apparatus comprising:
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a clock, operative at said sampling rate; a numerically controlled oscillator operative at periods T; an interpolator receiving samples at said sampling rate; and a loop filter, coupled to said interpolator and said numerically controlled oscillator and having an output responsive to a difference between said periods T and said period corresponding to said received symbol rate of said sampled signals, wherein said loop filter accepts an in phase component of said interpolated samples and an error signal is computed according to the equation;
##EQU15## wherein I is the in phase component;T is the symbol period; and r is the interval between alternate samples; wherein said numerically controlled oscillator is responsive to said output of said loop filter and generated an output signal that is representative of an interpolation distance between succeeding samples, and said interpolator interpolates said received samples according to said interpolation distance, and produces an output signal representative of interpolated samples. - View Dependent Claims (28, 29, 30)
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26. A signal processing apparatus for processing signals that are sampled by a sampler operative at a sampling rate, the signals having a period corresponding to a received symbol rate, the apparatus comprising:
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a clock, operative at said sampling rate; a numerically controlled oscillator operative at periods T; an interpolator receiving samples at said sampling rate; and a loop filter, coupled to said interpolator and said numerically controlled oscillator and having an output responsive to a difference between said periods T and said period corresponding to said received symbol rate of said sampled signals; wherein said numerically controlled oscillator is responsive to said output of said loop filter and generates an output signal that is representative of an interpolation distance between succeeding samples, and said interpolator interpolates said received samples according to said interpolation distance, and produces an output signal representative of interpolated samples wherein said loop filter accepts an in phase component and a quadrature component of said interpolated samples and said error signal is computed according to the equation;
##EQU16## wherein I is the in phase component;Q is the quadrature component; T is the symbol period; and r is the interval between alternate samples.
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27. A signal processing apparatus for processing signals that are sampled by a sampler operative at a sampling rate, the signals having a period corresponding to a received symbol rate, the apparatus comprising:
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a clock, operative at said sampling rate; a numerically controlled oscillator operative at periods T; an interpolator receiving samples at said sampling rate, wherein said interpolator is a sinc interpolator and performs a plurality of sinc interpolations that precede and follow a required sinc interpolation point; a linear interpolator that performs linear interpolation on said plurality of sinc interpolations; a loop filter, coupled to said interpolator and said numerically controlled oscillator and having an output responsive to a difference between said periods T and said period corresponding to said received symbol rate of said sampled signals; wherein said numerically controlled oscillator is responsive to said output of said loop filter and generates an output signal that is representative of an interpolation distance between succeeding samples, and said interpolator interpolates said received samples according to said interpolation distance, and produces an output signal representative of said interpolated samples.
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31. A signal processing apparatus for processing an input signal having a period corresponding to a received symbol rate, the apparatus comprising:
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a clock, operative at said sampling rate; a numerically controlled oscillator operative at periods T; a sinc interpolator receiving samples at said sampling rate;
wherein said interpolator comprises a finite impulse response filter operable according to a bank of coefficients, and an addressable memory having said coefficients memorized therein, wherein said sinc interpolator and performs a plurality of sinc interpolations that precede and follow a required sinc interpolation point;a linear interpolator that performs linear interpolation on said plurality of sinc interpolations; a loop filter, coupled to said sinc interpolator and said numerically controlled oscillator and having an output responsive to a difference between said periods T and said period corresponding to said received symbol rate of said sampled signals; a sampler, comprising first and second analog-to-digital converters respectively coupled to an in phase component and a quadrature component of said signals;
wherein said sinc interpolator and said loop filter accept in phase and quadrature outputs of said sampler;wherein said numerically controlled oscillator is responsive to said loop filter and generates an output signal that is representative of an interpolation distance between succeeding samples, and said interpolator interpolates said received samples according to said interpolation distance, and produces an output signal representative of interpolated samples; and
said numerically controlled oscillator, said sinc interpolator, and said loop filter comprise an integrated semiconductor circuit.
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Specification