Decision feedback equalizer with a pattern detector

A decision feedback equalizer for receiving a signal which includes a pulse transmission of a period of T seconds, an eliminating an intersymbol interference signal from the received signal, said equalizer comprising:

• adaptive filter means (50) responsive to a demodulated data sequence and N sample signals for estimating the intersymbol interference signal which occurs during the pulse transmission of T seconds and producing an estimated intersymbol interference signal comprising N individual estimated intersymbol interference signals, wherein N is a number;
• subtraction means (2) for subtracting the estimated intersymbol interference signal from the received signal to produce a residual signal;
• means (9) for extracting a residual intersymbol interference signal from the residual signal and a delayed residual signal which is produced by delaying the residual signal;
• demodulating means (3) for producing the demodulated data sequence from the residual signal;
• pattern detector means (11) for detecting a particular consecutive pattern out of the demodulated data sequence;
• a first selector means (10) for outputting one of the residual intersymbol interference signal and a reference signal in response to an output of said pattern detector means;
• a second selector means (13) for outputting one of the residual signal and the output of said first selector means in response to the demodulated data sequence;
• first sampling switch means (14) for selectively connecting, at periods of T/N, the output of said first selector means, the output of said second selector means, and the residual signal to said adaptive filter means so as to connect said adaptive filter means with the N sample signals during T seconds;
• and
• means for applying the N individual estimated intersymbol interference signals sequentially to said subtraction means at a period of T/N.

A decision feedback equalizer for receiving a signal which includes a pulse transmission of a period of T seconds, and eliminating an intrasymbol interference signal and an intersymbol interference signal from the received signal, said equalizer comprising:

• first adaptive filter means (50) responsive to a first demodulated data sequence and N sample signals for estimating the intersymbol interference signal which occurs during the pulse transmission of T seconds and producing an estimated intersymbol interference signal, wherein N is a number;
• means (2) for subtracting a total estimated interference signal from the received signal to produce a residual signal;
• means (9) for extracting a residual intersymbol interference signal from the residual signal and a delayed residual signal which is produced by delaying the residual signal;
• a first demodulating means (3) for producing the first demodulated data sequence from the residual signal;
• pattern detector means (11) for detecting a particular consecutive pattern out of the first demodulated data sequence;
• a first selector means (10) for outputting one of the residual intersymbol interference signal and a first reference signal in response to an output of said pattern detector means;
• first sampling switch means (16) receiving the residual signal for outputting the residual signal at a first time T/N, a second time 2T/N and a third time T;
• a second selector means (13) for outputting one of the residual signal produced by said first sampling switch means at said second time and an output of the first selector means in response to the first demodulated data sequence;
• second sampling switch means (14) for selectively connecting, at periods of T/N, the output of said first selector means, the output of said second selector means, and the residual signal produced by the first sampling switch means at said third time so as to connect the first adaptive filter means with the N sample signals during T seconds;
• a third selector means (17) for selectively outputting one of the residual signal produced by said first sampling switch means at said second time and a second reference signal in response to the first demodulated data sequence;
• second adaptive filter means (18) responsive to the residual signal produced by said first sampling switch means at said first time and the output of said third selector means for outputting a first partial estimated intrasymbol interference signal;
• second demodulating means (19) for outputting a second demodulated data sequence from the residual signal;
• third adaptive filter means (20) responsive to said second demodulated data sequence and the residual signal produced by said first sampling switch means at said third time for outputting a second partial estimated intrasymbol interference signal;
• and
• means (21, 22) for adding the estimated intersymbol interference signal, the first partial estimated intersymbol interference signal, and the second partial estimated intrasymbol interference signal to produce the total estimated interference signal.