Pulse or digital communications – Repeaters – Testing
Patent
1990-10-30
1992-10-20
Safourek, Benedict V.
Pulse or digital communications
Repeaters
Testing
375101, 370 321, 333 18, 379410, H03H 730, H03H 740
Patent
active
051576902
ABSTRACT:
An adaptive convergent decision feedback equalizer apparatus and method is disclosed for reducing intersymbol interference (ISI) in a data communication system. ISI is cancelled by generating and subtracting an estimation of the interference from a received signal. the estimation is generated by a N-tap transversal filter in which individual delayed received signals stored in the taps are multiplied by the respective adaptable tap coefficient and summed to form a digital representation of the ISI present. The present invention takes two steps to reduce the probability of coefficient adaptation from diverging. First, the DFE performs a coefficient modification only when the delayed received signal is a particular filter tap is a maximum or minimum level of the selected line code. A second step to eliminate divergence addresses the start up coefficient determination and errors in ISI estimation as the filter coefficients grow in size. On start up, only the first P number of DFE taps are chosen for modification and the remaining taps are held at zero. P is a number of taps for which the sum of the uncancelled ISI and the voltage error of an incorrect ISI estimation yields less than 0.5 probability of an error. After a minimum time (t.sub.min) which insures convergence, the remaining taps (N-P) are enabled.
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Level One Communications Inc.
Safourek Benedict V.
Tse Young T.
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