Adaptive transmit pre-emphasis for digital modem computed from noise spectrum
DC CAFCFirst Claim
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1. An apparatus for calculating pre-emphasis coefficients for a transmitting modem in a communications system, including:
- first transmitting means in the transmitting modem, including adjusting means responsive to the pre-emphasis coefficients for adjusting frequency-dependent characteristics of an output of said first transmitting means;
receiving means for receiving said output from said first transmitting means;
generating means for generating parameters responsive to a noise spectrum of said output including means for calculating said noise spectrum of said output;
second transmitting means for transmitting said parameters to the transmitting modem, andcomputing means for computing the pre-emphasis coefficients from said parameters.
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Abstract
An apparatus and method calculates pre-emphasis coefficients for a transmitting modem based upon the noise spectrum as it is received at the receiving modem. A noise spectrum analysis circuit calculates a difference between the best-fit transmitted data and the actually received data. This difference is used to compute a discrete Fourier transform of the noise spectrum, which is transmitted back to the transmitting modem on the secondary channel. This data is used to calculate filter coefficients for the transmitting modem.
88 Citations
21 Claims
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1. An apparatus for calculating pre-emphasis coefficients for a transmitting modem in a communications system, including:
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first transmitting means in the transmitting modem, including adjusting means responsive to the pre-emphasis coefficients for adjusting frequency-dependent characteristics of an output of said first transmitting means; receiving means for receiving said output from said first transmitting means; generating means for generating parameters responsive to a noise spectrum of said output including means for calculating said noise spectrum of said output; second transmitting means for transmitting said parameters to the transmitting modem, and computing means for computing the pre-emphasis coefficients from said parameters. - View Dependent Claims (2, 3, 4, 5, 15, 16, 17, 18, 19, 20)
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6. An apparatus for calculating pre-emphasis coefficients for a transmitting modem in a communications systems, including:
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first transmitting means in the transmitting modem, including adjusting means responsive to the pre-emphasis coefficients for adjusting frequency-dependent characteristics of an output of said first transmitting means; receiving means for receiving said output from said first transmitting means; generating means, including a noise spectrum generator circuit, for generating parameters responsive to a noise spectrum of said output; second transmitting means for transmitting said parameters to the transmitting modem; and computing means for computing the pre-emphasis coefficients from said parameters; wherein said noise spectrum generator circuit includes determining means for determining best-fit transmitted data points from said output of said first transmitting means as received by said receiving means; and
comparing means for determining a difference between said best-fit transmitted data points and said output as received by said receiving means;wherein said receiving means includes analog-to-digital conversion means and demodulating means which generates a complex signal; and
wherein said noise spectrum generator circuit includes a phase corrector responsive to said complex signal;
a slicer which determines, from said complex signal, best-fit transmitted data points from said first transmitted means;
subtracting means for determining a difference between said best-fit transmitted data points and said complex signal;
an inverse phase corrector responsive to said difference; and
a complex discrete Fourier transform block responsive to said inverse phase corrector. - View Dependent Claims (7)
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8. An apparatus for calculating pre-emphasis coefficients for a transmitting modem in a communications systems, including:
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first transmitting means in the transmitting modem, including adjusting means responsive to the pre-emphasis coefficients for adjusting frequency-dependent characteristics of an output of said first transmitting means; receiving means for receiving said output from said first transmitting means; generating means, including a noise spectrum generator circuit, for generating parameters responsive to a noise spectrum of said output; second transmitting means for transmitting said parameters to the transmitting modem; and computing means for computing the pre-emphasis coefficients from said parameters; wherein said noise spectrum generator circuit includes determining means for determining best-fit transmitted data points from said output of said first transmitting means as received by said receiving means; and
comparing means for determining a difference between said best-fit transmitted data points and said output as received by said receiving means; andwherein said determining means includes eye pattern data. - View Dependent Claims (10, 11, 12, 13, 14)
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9. An apparatus for calculating pre-emphasis coefficients for a transmitting modem in a communications systems, including:
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first transmitting means in the transmitting modem, including adjusting means responsive to the pre-emphasis coefficients for adjusting frequency-dependent characteristics of an output of said first transmitting means; receiving means for receiving said output from said first transmitting means; generating means, including a noise spectrum generator circuit, for generating parameters responsive to a noise spectrum of said output; second transmitting means for transmitting said parameters to the transmitting modem; and computing means for computing the pre-emphasis coefficients from said parameters; wherein said noise spectrum generator circuit includes determining means for determining best-fit transmitted data points from said output of said first transmitting means as received by said receiving means; and
comparing means for determining a difference between said best-fit transmitted data points and said output as received by said receiving means; andwherein said generating means includes discrete Fourier transform means responsive to said difference, thereby calculating a frequency domain representation of said noise spectrum of said output.
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21. A method for calculating pre-emphasis coefficients for a transmitting modem in a communications systems, including the steps of:
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transmitting from the transmitting modem; adjusting frequency characteristics of output from said transmitting step responsive to the pre-emphasis coefficients; receiving said output from said first transmitting means; calculating a noise spectrum of said output; generating parameters responsive to said noise spectrum of said output; sending said parameters to the transmitting modem; and computing the pre-emphasis coefficients from said parameters.
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Specification