Sign 3 ‐LMS data‐transition decision feedback equaliser

This study presents an adaptive data‐transition decision feedback equaliser (DT‐DFE) with a sign 3 least‐mean‐square (LMS) tap adaptation. Commonly used data‐state (DS) DFE suffers from reduced vertical eye‐opening when consecutive 1's or 0's are encountered. The proposed DT‐DFE performs DFE only when a data transition is detected. It boosts the eye‐opening of the high‐frequency components of data without attenuating the low‐frequency components of data whereas DS‐DFE boosts the eye‐opening of the high‐frequency components of data at the expense of the attenuated low‐frequency components of data. The reference voltages of DS‐DFE is tap‐dependent whereas those of DT‐DFE are tap‐independent and are obtained by conveying consecutive 1's and 0's to the channel in a training phase. The proposed DT‐DFE utilises loop unrolling to detect the occurrence of data transition. The performance of the proposed DT‐DFE is compared with that of DS‐DFE using two 5 Gbps backplane serial links designed in a TSMC 65 nm CMOS technology. Simulation results demonstrate that the eye‐opening of the link with DT‐DFE is 1.54 times that with DS‐DFE. The vertical eye‐opening of the link with DT‐DFE activating tap adaptation on two consecutive state transitions of opposite polarities is 1.2 times that that activates tap adaptation on single state transition. The proposed DT‐DFE is less sensitive to process uncertainty whereas DS‐DFE is prone to process uncertainty with severely deteriorating performance.