Equalization system with preshaping filter

Pulse or digital communications – Repeaters – Testing

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333 18, 364724, H04B 304

Patent

active

042837880

ABSTRACT:
An equalization system for eliminating precursor and postcursor interference effects from an incoming train of digital pulses comprises a cascade of decision stages interleaved with correction units emitting precursor-compensation signals to immediately following digital adders for algebraic combination with the incoming digital pulse train received thereby from a cascade of delay lines, the adders feeding the resulting precursor-compensated signals to respective decision stages. Postcursor compensation may be at least partially accomplished in a Viterbi or Ungerboeck receiver forming one of the decision stages or may be performed in an equalization cell having a correction unit transmitting postcursor-compensation signals to a digital adder inserted in the cascade of delay lines for substantially eliminating postcursor interference permanently. The cascade of decision stages may be preceded by a preshaping filter designed to reduce the amplitude of an incoming signal having a peak at an instant t(0) to a near-zero value at an instant t(0)+T, where T is the recurrence period of the incoming digital pulse train.

REFERENCES:
patent: 3614623 (1971-10-01), McAuliffe
patent: 3648171 (1972-03-01), Hirsch
patent: 3696203 (1972-10-01), Leonard
patent: 3798576 (1974-03-01), Torpie et al.
patent: 3984789 (1976-10-01), Luvison et al.
Article by A. Desblache and J. Tarrieu, entitled "Fast Adaptive Equalizer for Maximum Likelihood Sequence Estimation", IBM Technical Disclosure Bulletin, vol. 20, No. 10, pub. Mar. 1978, pp. 3953-3956.
Article by G. David Forney, Jr., entitled "Maximum-Likelihood Sequence Estimation of Digital Sequences in the Presence of Intersymbol Interference", IEEE Transactions on Information Theory, vol. IT-18, No. 3, pub. May 1972, pp. 363-378.
Article by Gottfried Ungerboeck, entitled "Adaptive Maximum-Likelihood Receiver for Carrier-Modulated Data-Transmission Systems", IEEE Transactions on Communications, vol. COM-22, No. 5, pub. May 1974, pp. 624-636.

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