A Sampled Analog MOS LSI Adaptive Filter

A novel realization of an adaptive filter using sampled analog MOS LSI techniques is described in this paper. The basic functional block of the adaptive filter is an electrically programmable transversal filter whose tap weights are modified according to the least mean square algorithm. A comparison has been made among different available approaches for implementing a programmable transversal filter. A rotating tap weight structure [1] has been used to realize a 32-tap programmable transversal filter with features for the adaptive operation included on an NMOS silicon-gate chip. The adaptive filter has been characterized as a parameter estimator which finds application in echo cancellation and noise cancellation. A wide range of magnitude and phase characteristics of the unknown system (to be modeled by the adaptive filter) have been used to test the performance of the present adaptive system. Results on the residual error and the convergence time under different conditions are reported. Some practical limitations of the system are also presented.