A Novel Analog Decision-Feedback Equalizer in CMOS for Serial 10-Gb/sec Data Transmission Systems

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Chandramouli, Soumya
Laskar, Joy
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This dissertation develops an unclocked receiver analog decision-feedback equalizer (ADFE) circuit architecture and topology and implements the circuit in 0.18-um CMOS to enable 10-Gb/sec serial baseband data transmission over FR-4 backplane and optical fibre. The ADFE overcomes the first feedback-loop latency challenge of traditional digital and mixed-signal DFEs by separating data re-timing from equalization and also eliminates the need for clock-recovery prior to decision-feedback equalization. The ADFE enables 10-Gb/sec decision-feedback equalization using a 0.18-um CMOS process, the first to do so to the author s knowledge. A tuneable current-mode-logic (CML) feedback-loop is designed to enable first post-cursor cancellation for a range of data-rates and to have external control over loop latency over variations in process, voltage and temperature. CML design techniques are used to minimize current consumption and achieve the required voltage swing for decision-feedback to take place. The all-analog equalizer consumes less power and area than comparable state-of-the art DFEs. The ADFE is used to compensate inter-symbol interference (ISI) for 20 inches of FR-4 backplane and 300 m of multi-mode fibre at 10-Gb/sec. The ADFE also extends the reach of single-mode fibre at 10-Gb/sec to 120 km. The work described in this dissertation advances the state-of-the-art in equalization solutions for multi-Gb/sec serial data transmission and can find applications in several of the 10-Gb/sec Ethernet standards that have been approved recently. The contributions of this work toward future research are also discussed.
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