Crosstalk Suppression Technique for Multi-Wire High-Speed I/O Links

Tzu-Chien Hsueh
Advisor: Sudhakar Pamarti

Thursday, May 13, 2010 at 2:00pm
Engr. IV Maxwell Room 57-124

Abstract:
The use of differential-mode (DM) signaling in modern high-speed serial data communication systems has enabled multiple Gb/s data rates. To sustain the growth of I/O bandwidth requirements, raising the signaling frequency of the DM links and the number of package I/O pins poses tremendous challenges because of the harsh signaling environment of FR4 printed circuit boards and the costs of die areas and IC packages. Simultaneous differential-mode and common-mode signaling (henceforth referred to as CM signaling) can improve pin utilization and aggregate data bandwidth without increasing the signaling frequency of the high-speed transceivers. However, because inevitable transmission-line and circuit mismatches could cause signal crosstalk between the DM and CM links, the achievable data bandwidth and power efficiency of CM signaling are seriously limited.

A crosstalk cancellation technique based on the Code Division Multiple Access (CDMA) principles was proposed to suppress crosstalk in CM signaling systems. The technique effectively up-converts the crosstalk spectrum and suppresses in-band crosstalk power by using a simple analog variant of CDMA. This concept has been verified by a CDMA-based four-wire signaling transceiver in a 90 nm standard CMOS technology. The transceiver achieved 16 Gb/s aggregate data rate (5.33 Gb/s/link) and 6 mW/Gb/s/wire power efficiency over four 6" FR4 PCB traces with BER <10-12. Compared to conventional CM signaling systems, the CDMA-based system provides 30x ~ 100x improvement in BER.

The primary focus of this talk is on the operation of this CDMA-based system, its limitations, implementation, and measurement results. Furthermore, this talk briefly describes the analysis of crosstalk due to circuit and channel mismatches. Based on the crosstalk analysis, simplified mathematic expressions are derived to reasonably estimate the crosstalk power in both CM signaling and CDMA-based systems. The estimation results are consistent with time-domain simulations using realistic channel models. This crosstalk analysis approach can be applied to any NRZ high-speed serial link I/O system as long as the frequency domain responses of crosstalk conversion or coupling paths can be reasonably characterized.

Biography:
Tzu-Chien Hsueh received the B.S. and M.S. degrees in electrical engineering from National Taiwan University, Taipei, Taiwan in 1999 and 2001, respectively. He is currently working toward the Ph.D. degree in electrical engineering at University of California, Los Angeles, CA. From 2001 to 2006, he was a design engineer with Silicon Integrated Systems Corp. and Chip Advanced Technology Corp., Hsinchu, Taiwan, working on Delta-Sigma A/D converters and Gigabit Ethernet I/O systems. His research interests include high-speed mixed signal circuits, I/O links, and data converters.