A pole-zero-tracking constant modulus algorithm

An approach to multipath correction in FM transmission is proposed. It is based on the factorization of the channel transfer function in terms of the roots of the underlying polynomial. A time-recursive algorithm for the identification of the roots of the all-zero channel transfer function at the receiver is presented. It allows an efficient adaptive design of special equalizer structures with low computational burden compared to existing solutions. The multipath correction method was tested in connection with a baseband FM receiver and a modulating signal consisting of a bandlimited stereo-multiplex signal produced by combining sinusoids with random phases distributed uniformly in the interval 0-2π. The identification of the channel roots was accomplished by means of a stochastic gradient algorithm with constant step size α=0.0005. The trajectories of the identified roots in the z-plane and the corresponding modulus of the equalizer output signal are illustrated for three different channel configurations