US 6,816,204 B2Granted

Ghost cancellation reference signals for broadcast digital television signal receivers and receivers for utilizing them

OwnerAllen Le Roy Limberginventor

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Abstract

Broadcast DTV signals are improved by including in each of their successive data fields a training signal for the adaptive channel-equalization and echo-cancellation filtering in receivers. The training signal in each data field includes a prescribed number of cycles of a particular pseudo-random noise sequence extending over a plurality of data segments to provide a training signal for the adaptive filtering that is of longer duration than one of said data segments. Each data segment in each data field begins with a data segment synchronizing sequence, and the training signals incorporate some of these data segment synchronizing sequences within themselves. Receivers are described that initialize the parameters of the adaptive filtering using discrete Fourier transform calculations on the training signal, and receivers are described that initialize the parameters of the adaptive filtering using the results of match filtering for the particular pseudo-random noise sequence.

Claims23

Dependent claims

A method of structuring each of a succession of consecutive, non-overlapping data fields for digital television broadcasting to at least one receiver having adaptive equalization and echo suppression filtering therein, said method comprising steps of:

dividing each said data field into a prescribed number of successive data segments, each containing a prescribed number of plural-modulation-level symbols;
and
beginning each data segment with a respective data segment synchronizing sequence of common type, which data segment synchronizing sequence is composed entirely of symbols of first and second modulation levels as used in said plural-modulation-level symbols;
said method being improved to comprise a further step of:
including, within each of periodically occurring groups of at least two consecutive data segments in said succession of consecutive data fields, a prescribed number of consecutive cycles at least two of a repetitive pseudo-random noise sequence composed entirely of symbols each of one of said first and said second modulation levels, said repetitive pseudo-random noise sequence extending into each of the data segments of that one of said groups of at least two consecutive data segments in which said repetitive pseudo-random noise sequence is included, and said consecutive cycles of said repetitive pseudo-random noise sequence subsuming therewithin each said data segment synchronizing sequence of said common type between the consecutive data segments in that said one of said groups of at least two consecutive data segments in which said repetitive pseudo-random noise sequence is included.

2 more elements

A receiver for digital television signals, said receiver comprising:

front-end circuitry for supplying an amplified intermediate-frequency signal responsive to a radio-frequency broadcast digital television signal selected for reception;
demodulator and analog-to-digital conversion circuitry for recovering a digitized baseband broadcast digital television signal from said amplified intermediate-frequency signal, said demodulator and analog-to-digital conversion circuitry connected for receiving said amplified intermediate-frequency signal from said front-end circuitry;
computer apparatus for computing the discrete Fourier transform of the power spectrum of a received signal from a set of successive digital samples thereof that are of prescribed number and prescribed sampling rate, generating from the power spectrum of said signal another discrete Fourier transform characterizing the actual transmission channel, and computing the inverse-Fourier transform of said discrete Fourier transform characterizing said actual transmission channel;
gating circuitry for selecting respective sets of successive digital samples to be supplied to said computer apparatus, each said set of successive digital samples being selected from the digitized baseband broadcast digital television signal recovered by said demodulator and analog-to-digital conversion circuitry, each said set of successive digital samples as so selected being of said prescribed number and said prescribed sampling rate;
and
adaptive channel-equalization and echo-cancellation filtering connected for responding to said digitized baseband broadcast digital television signal with a response that is adapted by adjustment of the weighting coefficients of said adaptive channel-equalization and echo-cancellation filtering in response to said inverse-Fourier transform.

3 more elements

A method of structuring each of a succession of consecutive, non-overlapping data fields in a digital television signal for broadcasting to at least one receiver having adaptive equalization and echo suppression filtering therein, said method comprising steps of:

dividing each said data field into a prescribed number of successive data segments, each containing a prescribed number of plural-modulation-level symbols;
forward-error-correction coding data to generate forward-error-correction coded data;
convolutionally interleaving said forward-error-correction coded data to generate convolutionally interleaved forward-error-correction coded data;
processing said convolutionally interleaved forward-error-correction coded data for inclusion in consecutive data segments within a prescribed first portion of each said data field beginning with a second one of its data segments immediately succeeding the initial first one of its data segments, said prescribed first portion of each said data field ending before the conclusion of that said data field;
beginning each data segment within said prescribed first portion of each said data field with a respective data segment synchronizing sequence of common type, which data segment synchronizing sequence consists of symbols of first and second modulation levels as used in said plural-modulation-level symbols;
beginning, within a concluding second portion of each said data field immediately succeeding said prescribed first portion thereof, a prescribed training signal that continues longer than a data segment and extends into the next of said succession of consecutive data fields, that is composed entirely of said plural-modulation-level symbols arranged in prescribed order, and that exhibits well-defined auto-correlation properties for essentially each and every 511-symbol-epoch portion thereof;
and
concluding said prescribed training signal within a first data segment of the next of said succession of consecutive data fields, the portion of said prescribed training signal within the first data segment of each said data field including at least one 511-symbol cycle of a particular maximal-length pseudo-random noise sequence that is composed entirely of symbols of first and second modulation levels as used in said plural-modulation-level symbols.

5 more elements

Dependencies are inferred from the claim text.

Facts

Application: 09/765,019Filed 18 Jan 2001 · us provisional application
Priority: 19 Jan 2000
Published: US 2001/0033341 A125 Oct 2001
Granted: 9 Nov 2004
Term ends: Not estimatedThe source records don’t support an estimate.

Classification8 codes

H04N 5/211
Circuitry for suppressing or minimising disturbance, e.g. moiré or halo: ghost signal cancellation
H04L 2025/03375
Characterised by the type of transmission: passband transmission
H04L 2025/0349
Time-recursive: as a feedback filter
H04L 2025/03617
Iterative algorithms: time recursive algorithms