US5311546A — Carrier phase recovery for an adaptive equalizer

Claim 1

Independent Claim 99 words

A method for adaptively equalizing data signals in a communications receiver comprising the steps of: demodulating an unequalized data signal; filtering said demodulated data signal in an adaptive equalizer that initially updates adaptive filter coefficients using error signals derived from a first coefficient update algorithm; generating a carrier lock signal when a phase error of a filtered signal output from said adaptive equalizer reaches a threshold value; and updating said adaptive filter coefficients in said adaptive equalizer using error signals derived from a second coefficient update algorithm instead of said first algorithm in response to said carrier lock signal.

Claim 2

Independent Claim 99 words

A method for adaptively equalizing data signals in a communications receiver comprising the steps of: demodulating an unequalized data signal; filtering said demodulated data signal in an adaptive equalizer that initially updates adaptive filter coefficients using error signals derived from a first coefficient update algorithm; generating a carrier lock signal when a phase error of a filtered signal output from said adaptive equalizer reaches a threshold value; and updating said adaptive filter coefficients in said adaptive equalizer using error signals derived from a second coefficient update algorithm instead of said first algorithm in response to said carrier lock signal.

Claim 3

Dependent Claim 46 words

A method in accordance with claim 1 comprising the further steps of: monitoring said phase error during the operation of said adaptive equalizer; and returning to said first algorithm if it is determined during said monitoring step that said phase error no longer meets said threshold.

Claim 4

Dependent Claim 17 words

A method in accordance with claim 1 wherein said first algorithm is a self recovering equalization algorithm.

Claim 5

Dependent Claim 18 words

A method in accordance with claim 3 wherein said self recovering equalization algorithm is a constant modulus algorithm.

Claim 6

Dependent Claim 16 words

A method in accordance with claim 3 wherein said second algorithm is a decision directed algorithm.

Claim 7

Dependent Claim 33 words

A method in accordance with claim 1 wherein said threshold value is reached when at least a minimum percentage of samples of said filtered signal taken over time fall within a predetermined range.

Claim 8

Dependent Claim 48 words

A method in accordance with claim 6 wherein: said demodulated data signal comprises coordinates representing an N-point constellation pattern for a demodulated N-bit quadrature amplitude modulated signal; and said range comprises a plurality of separate fixed areas, each area enclosing one of the points in said constellation pattern.

Claim 9

Dependent Claim 48 words

A method in accordance with claim 7 wherein each of said separate fixed ares comprises an ellipse surrounding one of the points in said constellation pattern, each ellipse being aligned with a corresponding radius extending from an origin of said constellation pattern to the point the ellipse surrounds.

Claim 10

Dependent Claim 169 words

An adaptive equalizer for a communications receiver comprising: means for demodulating an unequalized data signal; an equalizer loop containing a filter coupled to receive demodulated data from said demodulating means, an error signal generator coupled to receive filtered data from said filter, and means responsive to error signals from said error signal generator for updating coefficients for input to said filter; a carrier recovery loop comprising a phase detector coupled to receive said filtered data and provide a first phase error signal for controlling said demodulating means; and means, coupled to receive a second phase error signal from said phase detector, for generating a carrier lock signal when said second phase error signal meets a threshold; wherein said error signal generator is responsive to said carrier lock signal for generating error signals from a first coefficient update algorithm when said second phase error signal fails to meet said threshold and for generating error signals from a second coefficient update algorithm when said second phase error signal meets said threshold.

Claim 11

Dependent Claim 169 words

An adaptive equalizer for a communications receiver comprising: means for demodulating an unequalized data signal; an equalizer loop containing a filter coupled to receive demodulated data from said demodulating means, an error signal generator coupled to receive filtered data from said filter, and means responsive to error signals from said error signal generator for updating coefficients for input to said filter; a carrier recovery loop comprising a phase detector coupled to receive said filtered data and provide a first phase error signal for controlling said demodulating means; and means, coupled to receive a second phase error signal from said phase detector, for generating a carrier lock signal when said second phase error signal meets a threshold; wherein said error signal generator is responsive to said carrier lock signal for generating error signals from a first coefficient update algorithm when said second phase error signal fails to meet said threshold and for generating error signals from a second coefficient update algorithm when said second phase error signal meets said threshold.

Claim 12

Dependent Claim 39 words

An equalizer in accordance with claim 9 wherein said error signal generator comprises a memory storing a first set of error signals computer using said first algorithm and a second set of error signals computed using said second algorithm

Claim 13

Dependent Claim 26 words

An equalizer in accordance with claim 10 wherein said filtered data and said carrier lock signal are used to address said memory to output error signals.

Claim 14

Dependent Claim 17 words

An equalizer in accordance with claim 11 wherein said first algorithm is a self recovering equalization algorithm

Claim 15

Dependent Claim 18 words

An equalizer in accordance with claim 12 wherein said self recovering equalization algorithm is a constant modulus algorithm

Claim 16

Dependent Claim 16 words

An equalizer in accordance with claim 12 wherein said second algorithm is a decision directed algorithm.

Claim 17

Dependent Claim 34 words

An equalizer in accordance with claim 9 wherein said phase error threshold is met when at least a minimum percentage of samples of said filtered data taken over time fall within a predetermined range.

Claim 18

Dependent Claim 48 words

An equalizer in accordance with claim 15 wherein: said demodulated data signal comprises coordinates representing an N-bit point constellation pattern for a demodulated N-bit quadrature amplitude modulated signal; and said range comprises a plurality of separate fixed areas, each enclosing one of the points in said constellation pattern.

Claim 19

Dependent Claim 48 words

An equalizer in accordance with claim 16 wherein each of said separate fixed areas comprises an ellipse surrounding one of the points in said constellation pattern, each ellipse being aligned with a corresponding radius extending from an origin of said constellation pattern to the point the ellipse surrounds.

Claim 20

Dependent Claim 137 words

An adaptive equalizer for a communications receiver comprising: an adaptive filter for filtering unequalized data representative of coordinates in a constellation pattern; an error signal generator for converting filtered data from said filter to error signals based on a first or second coefficient update algorithm; means coupled to receive error signals output form said error signal generator for updating coefficients for said adaptive filter; a phase detector for converting said filtered data to phase error signals; and means responsive to said phase error signals for controlling said error signal generator to provide error signals according to said first coefficient update algorithm when a phase error represented by said phase error signals is above a predetermined threshold and to provide error signals according to said second coefficient update algorithm when said phase error is below said predetermined threshold.

Claim 21

Dependent Claim 137 words

An adaptive equalizer for a communications receiver comprising: an adaptive filter for filtering unequalized data representative of coordinates in a constellation pattern; an error signal generator for converting filtered data from said filter to error signals based on a first or second coefficient update algorithm; means coupled to receive error signals output form said error signal generator for updating coefficients for said adaptive filter; a phase detector for converting said filtered data to phase error signals; and means responsive to said phase error signals for controlling said error signal generator to provide error signals according to said first coefficient update algorithm when a phase error represented by said phase error signals is above a predetermined threshold and to provide error signals according to said second coefficient update algorithm when said phase error is below said predetermined threshold.

Claim 22

Dependent Claim 43 words

An equalizer in accordance with claim 18 wherein said error signal generator comprises a look up table containing error signal data computed under said first and second algorithms and addressed by said filtered data and said control means to output said error signals.

Claim 23

Dependent Claim 32 words

An equalizer in accordance with claim 18 wherein said phase detector comprises a look up table containing phase error data and addressed by said filtered data to output said phase error signals.

Annuity Stage	Window Opens	Payment Deadline	Surcharge Period Until	Estimated Fee	Status
3.5 Years (Year 4)	1997-05-09	1997-11-08	1998-05-10	$2000.00	Window Closed / Lapsed
7.5 Years (Year 8)	2001-05-09	2001-11-08	2002-05-10	$3760.00	Window Closed / Lapsed
11.5 Years (Year 12)	2005-05-09	2005-11-08	2006-05-10	$7700.00	Window Closed / Lapsed

Carrier phase recovery for an adaptive equalizer

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