No abstract

An adaptive Volterra linearizer for reducing channel nonlinearities in QAM data transmission systems is described and its performance is evaluated. The linearizer is implemented as a modem receiver digital circuit which employs two read-only memories that are programmed to cancel either third or fifth order nonlinearities. The memory outputs are scaled by adaptive coefficients which minimize the channel nonlinearity. In a 64-QAM digital radio system, the linearizer is shown to reduce nonlinear residual error rates by five orders of magnitude.