Nonlinear echo cancellers based on transpose distributed arithmetic

The design and performance of an echo canceller used in a full-duplex multilevel digital baseband transmission system are described. The system suffers from mild nonlinearity due to tolerancing of analog components in its transmitter. The nonlinearity is dealt with in the echo canceller by recourse to a nonlinear adaptive filter based on the use of transpose distributed arithmetic. Filter structures allowing fast startup techniques that use known bounds on the nonlinearities are evaluated. The theoretical performance of the filters is examined, and the extrapolation of classical linear theory is shown to provide an insufficient description of the filters´ behavior. A novel state-variable-analysis technique is introduced and shown to provide a complete description