Design of delta operator based decision feedback equalizer for high-speed backplane data communication

We implement a 3-tap quantizing delta operator based least mean square (DLMS) decision feedback equalizer (DFE) using mixed signal approach. The mixed signal design consists of the algorithm circuitry in the digital domain for easier implementation of the computational algorithm, and the filter circuitry in the analog domain for high-speed operation. The implementation of the delta operator loop in the analog filter is achieved by quantizing the signal using parallel current mode logic (CML) structures and low resolution analog to digital converters (ADC).;We show through system level simulation that the 3-tap DLMS DFE achieved 15% more eye opening in the eye diagram compared to the corresponding 3-tap least mean square (LMS) DFE. Using the same step size constant for different channels of length ranging from 10 to 25 inches, without optimizing for the channel, the DLMS DFE can still have 30% eye opening while the LMS DFE's eye is completely closed. Moreover, the 3-tap DLMS DFE achieved the same eye opening as a 5-tap LMS DFE.