A Novel Module-Sign Low-Power Implementation for the DLMS Adaptive Filter with Low Steady-State Error

In this paper, a novel implementation is proposed for the Delayed LMS (DLMS) filter, able to reduce the power dissipation while preserving regime performances. The approach relies on the observation that the error signal is small in magnitude and oscillates around zero when the circuit is close to the convergence point. Therefore, the most significant bits of the error signal continuously toggle from positive to negative values causing high switching activity in the multipliers of the feedback section. This paper proposes to employ a sign-modulus representation of the error signal, to substantially reduce the switching activity of the feedback path of the filter. Additional approximation techniques are also devised to further reduce power dissipation. Comparisons with the state-of-the-art show that the proposed filter is the only one able to approach the MSE of the exact implementation with a remarkable reduction of power dissipation. A test-chip in TSMC 28nm CMOS technology has been realized to experimentally verify the validity of our technique. The experimental results show the possibility of saving up to 45.4% of power consumption with respect to the exact implementation of the filter.