International Business Machines Corporation
Feedforward equalizer with programmable roaming taps

Abstract:

A transmitter (TX)-side feedforward equalizer (FFE) includes one or more "roaming" filter taps which can be used to compensate reflections that occur at unpredictable and substantial time offsets from a main pulse. The roaming filter taps are realized in a hardware- and power-efficient manner by implementing a programmable delay serializer in which the phases of multi-rate clocks are switched to introduce binary weighted delays on the roaming tap. In this way a variable difference in latencies is introduced between the main and the roaming tap data paths. The TX-side FFE implementations provide a fully programmable roaming tap generator having a 1-Unit Interval (UI) resolution of delay setting integrated into the data serializer of the TX macro.