Pulse or digital communications – Repeaters – Testing
Patent
1981-12-24
1983-08-16
Masinick, Michael A.
Pulse or digital communications
Repeaters
Testing
375 14, 375 12, 333 18, H04B 116
Patent
active
RE0313513
ABSTRACT:
A receiver for a quadrature amplitude modulated data signal impaired by linear and nonlinear distortion, phase jitter and additive noise includes circuitry which compensates for these impairments. In particular, the receiver includes a processor (FIG. 1 44; FIG. 2, 44') which subtracts a feedback nonlinear signal (FIG. 1, D(n); FIG. 2, D'(n)) from each sample of the received signal, either prior or subsequent to demodulation, providing compensation for nonlinear intersymbol interference. The feedback nonlinear signal subtracted from each sample is comprised of a weighted sum of products of individual data decisions and/or the complex conjugates of data decisions, each such product, in turn, being multiplied by a predetermined harmonic of the carrier frequency. In an illustrative embodiment, compensation for second- and third-order intersymbol interference is provided by including two- and three-multiplicand weighted products in the feedback nonlinear signal. Weighting coefficients for each product are adaptively updated in a decision-directed manner.
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Bell Telephone Laboratories Incorporated
Masinick Michael A.
Slusky Ronald D.
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