Passband equalizer for a vestigial sideband signal receiver
AssigneesSarnoff Corporation, Motorola, Inc.
InventorsMehmet Vakif Tazebay, Randall Bret Perlow
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Abstract
A passband equalizer that performs blind equalization upon a complex signal, e.g., a vestigial sideband (VSB) signal, without using a training sequence. The passband equalizer contains a decision directed equalizer (DFE) that operates upon separate in phase (I) and quadrature phase (Q) signals using a filter for the I signal and a filter for the Q signal without using filters for cross components of the I and Q signals. As such, the DFE contains approximately half of the multipliers and adders that are used in prior art DFEs.
Claims22
A passband equalizer comprising:
- a feed forward equalizer containing at least one equalization filter;
- a decision feedback equalizer that is supplied with separate in-phase and quadrature components of a complex signal containing a first adaptive filter for only filtering the in-phase (I) component and a second adaptive filter for only filtering the quadrature (Q) component without filtering a cross-coupled component of the complex signal;
- and
- a summer for summing an output of the feed forward equalizer with an output of the decision feedback equalizer.
An adaptive filter for filtering vestigial sideband (VSB) signals that have a symbol duration of T, the filter comprising:
- a plurality of complex multipliers, where each multiplier is separated from each other complex multiplier by a time delay element having a delay of 2T, where T is a symbol period of a symbol within the complex signal, and each complex multiplier multiplies a delayed input signal with a complex weighting value to produce a weighted signal, wherein the time delay element contains a first delay element and a second delay element and the adaptive filter further comprises a switch for bypassing the first delay element to change the 2T-spaced filter into a T-spaced filter;
- and
- a combiner for adding the weighted values to produce an equalized signal.
An adaptive filter for filtering vestigial sideband (VSB) signals that have a symbol duration of T, the filter comprising:
- a plurality of complex multipliers, where each multiplier is separated from each other complex multiplier by a time delay element having a delay of 2T, where T is a symbol period of a symbol within the complex signal, and each complex multiplier multiplies a delayed Input signal with a complex weighting value to produce a weighted signal, wherein each complex multiplier contains four real multipliers that are selectively arranged to form a T-spaced real filter by having a first pair of real multipliers connected to a first time delay element and a second pair of real multipliers connected to a second time delay element;
- and
- a combiner for adding the weighted values to produce an equalized signal.
A selectable adaptive filter for filtering vestigial sideband (VSB) signals that have a symbol duration of T, the filter comprising:
- a plurality of complex multipliers, where each complex multiplier is separated from each other complex multiplier by a time delay element having a delay of 2T, where T is a symbol period of a symbol within the complex signal, and each complex multiplier multiplies a delayed input signal with a weighting value to produce a weighted signal;
- a combiner for adding the weighted values to produce an equalized signal;
- and
- where the time delay element contains a first delay element and a second delay element and the adaptive filter further comprises a switch for bypassing the first delay element to change the complex 2T-spaced filter into a complex T-spaced filter.
A digital television receiver comprising
- a tuner for selecting a digital television signal from a plurality of available digital television signals;
- an analog to digital converter for digitizing said selected digital television signal to produce a digitized signal;
- a pilot recovery circuit for recovering a pilot tone from said digitized signal;
- a timing recovery circuit for extracting symbol timing from the digitized signal;
- a Nyquist filter for extracting a complex signal from the digitized signal;
- a passband equalizer for adaptively filtering said complex signal, where said passband equalizer comprises:
- a feed-forward equalizer (FFE);
- and
- a decision feedback equalizer (DFE) that is supplied with separate in-phase and quadrature components of said complex signal containing a first adaptive filter for filtering the in-phase (I) component, a second adaptive filter for filtering the quadrature (Q) component, a combiner for combining the filter Q component with the filtered I component, and a delay for delaying the Q component for a duration equal to a delay through the first filter and the combiner.
Dependencies are inferred from the claim text.