A novel mixed-mode adaptive equalization system for high-speed 2-level PAM signals

摘要

A novel mixed-mode adaptive equalization system for a high-speed 2-level pulse-amplitude modulated (PAM) signal is presented. The intended application is in the area of digital serial interface, such as a non-return-to-zero-inverted (NRZI) serial video signal with a data rate of 2 7OMbitsls. The adaptive system tunes the zeros of a finite-impulse-response (FIR) analog programmable filter. Programmable differentiators and transconductors are designed to increase the tuning range of the filter. An average error obtained by calculating the accumulated area of the eye-diagram, and average gradients are proposed as inputs to a digital least-mean-squared (LMS) algorithm. This approach allows a more relaxed speed requirement for analog-to-digital converters (ADCs). A third-order analog filter, along with some essential circuit blocks, are designed for a 0.35μm CMOS process.