Two stage equalizer for trellis coded systems

For use in a receiver capable of decoding trellis encoded signals, a two stage decision feedback equalizer in which forward filter coefficients, fk, remain constant for the duration of D symbols, said two stage decision feedback equalizer comprising a forward equalizer filter, a first decision feedback equalization filter, a trellis decoder, a delay buffer, and a second decision feedback equalization filter

• wherein said first decision feedback equalization filter is coupled to each path memory output of said trellis decoder, said first decision feedback equalization filter capable of obtaining symbol values from each path memory output of said trellis decoder for use as an estimate in channel equalization;
• wherein an input of said second stage decision feedback equalization filter is coupled to an output, ak, of said trellis decoder;
• wherein an output signal, Bk, of said forward equalizer filter is provided to said delay buffer and said delay buffer delays said signal for a duration of D symbols;
• and
• wherein an output signal, bk, of said delay buffer is added to an output signal of said second feedback decision equalization filter to form an output signal, yk, for said two stage decision feedback equalizer.

A high definition television receiver capable of decoding trellis encoded signals comprising a two stage decision feedback equalizer comprising:

• a first stage equalizer comprising a first forward equalizer filter, a first decision feedback equalization filter, and a trellis decoder,
• wherein said first decision feedback equalization filter is coupled to each path memory output of said trellis decoder, said first decision feedback equalization filter capable of obtaining symbol values from each path memory output of said trellis decoder for use as an estimate in channel equalization;
• and
• a second stage equalizer coupled to said first stage equalizer, said second stage equalizer comprising a second forward equalizer filter, and a second decision feedback equalization filter,
• wherein an input of said second stage decision feedback equalization filter is coupled to an output of said trellis decoder.

A high definition television receiver comprising a two stage decision feedback equalizer in which forward filter coefficients, fk, remain constant for the duration of D symbols, said two stage decision feedback equalizer comprising a forward equalizer filter, a first decision feedback equalization filter, a trellis decoder, a delay buffer, and a second decision feedback equalization filter

• wherein said first decision feedback equalization filter is coupled to each path memory output of said trellis decoder, said first decision feedback equalization filter capable of obtaining symbol values from each path memory output of said trellis decoder for use as an estimate in channel equalization;
• wherein an input of said second stage decision feedback equalization filter is coupled to an output, ak, of said trellis decoder;
• wherein an output signal, Bk, of said forward equalizer filter is provided to said delay buffer and said delay buffer delays said signal for a duration of D symbols;
• and
• wherein an output signal, bk, of said delay buffer is added to an output signal of said second feedback decision equalization filter to form an output signal, yk, for said two stage decision feedback equalizer.

For use in a receiver capable of decoding trellis encoded signals, a method for reducing error in a two stage decision feedback equalizer comprising the steps of:

• obtaining an estimate of a symbol stream using a first stage equalizer comprising a first forward equalizer filter, a first decision feedback equalization filter, and a trellis decoder;
• and
• providing said estimate of said symbol stream to a second stage equalizer comprising a second forward equalization filter and a second decision feedback equalization filter;
• minimizing error is said second stage equalizer using decisions from said trellis decoder.