A continuous-time adaptive filter structure

Adaptive filters have been traditionally developed in a digital environment which involves a large number of computations to derive the coefficients of the desired approximation. Most of the time, these calculations required a machine of great capacity and that is not practical for some applications like channel equalization in cellular systems. This paper proposes a continuous-time adaptive filter which is based on representing the impulse response of an adaptive filter as a linear combination of a set of orthogonal exponentials. An important practical advantage is that if a satisfactory representation can be obtained by exponentials simple filter structures can be synthesized. An analog adaptive filter structure that improve the time convergence of conventional realizations using a continuos time LMS algorithm to reduce the error between the reference system and the adaptive filter is shown.