Transmitter Equalization for 4-Gb/s Signaling

William J. Dally
Massachusetts Institute of Technology

John Poulton
University of North Carolina - Chapel Hill

To operate a serial channel over copper wires at 4 Gb/s, we incorporate an 4-GHz FIR equalizing filter into a differential transmitter. The equalizer cancels the frequency-dependent attenuation caused by the skin-effect resistance of copper wire, giving a frequency response that is flat to within 5% over the band from 200 MHz to 2 GHz even over wires with 6 dB of high-frequency attenuation. All but the last stage of the transmitter operates at 400 MHz. The transmitter output stage uses a stable, 10-phase, 400-MHz clock to sequence an array of drivers that implement the FIR filter.

We introduce the concept of digital-signal equalization, describe the system design, and circuit design of our equalizing transmitter, and present simulation results from a 4-Gb/s 0.5-mm CMOS transmitter.

Keywords: Interconnects, transmission equalization, digital-signal equalization, circuit design

IEEE Micro, Vol. 17, No. 1, January / February 1997
Copyright (c) 1997 Institute of Electrical and Electronics Engineers, Inc. All rights reserved.

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