Design of adaptive equalizer for digital subscriber loop using 2B1Q code

An adaptive equalizer structure for a digital subscriber loop using 2B1Q code is presented to combat intersymbol interference (ISI). A shaping filter is introduced to eliminate the precursor ISI. The design of this adaptive equalizer is based on a decision feedback equalizer (DFE) structure without feedforward section employing a clipped least-mean-square algorithm for estimating the postcursor of the channel´s impulse response. A new variable stepsize method and a shape-oriented adjustment method are used to improve the convergence speed of the adaptive equalizer. Software simulation demonstrates the feasibility of the algorithm and structure. A hardware circuit is implemented using a logic cell array for real-time testing