BER-based adaptive ADC-equalizer based receiver for communication links

This paper presents the architecture of a non-uniform reference level bit error-rate (BER)-optimal analog-to-digital converter (ADC) and equalizer, for high-speed communication links. Finite precision analysis demonstrates that the use of the BER-optimal ADC does not increase the equalizer complexity/power significantly. An adaptive algorithm referred to as the approximate minimum BER algorithm (AMBER) is proposed in order to determine the BER-optimal reference levels. Finite-precision analysis of AMBER indicates that reference levels represented with 9-bit precision is sufficient for a 3-bit BER-optimal ADC to achieve BER equal to that of a 4-bit conventional ADC. An architectural implementation of AMBER is also presented. The reference-level adaptation unit (RL-UD) has a full-adder (FA) complexity that is 76% over the conventional adaptive equalizer. The RL-UD block is clock-gated after convergence and hence does not present a power overhead. Thus, for high-speed links employing the flash ADC architecture, the proposed AMBER receiver represents a power savings of approximately 50% in the ADC.