Silicon integrated adaptive LMS echo canceller with provision for variable step size

Custom silicon implementation of a data-driven adaptive echo-canceller, designed for 16QAM modulated signals, capable of handling data at 2400 Baud (CCITT V.32 standard) is presented. The configuration which was implemented is the so-called Nyquist in-band echo-canceller. Standalone it can perform near-echo cancellation but two devices can be put together in a master/slave configuration to operate as a complete echo-cancellation system for near and far-end echo cancellation. Our echo-canceller consists of adaptive FIR filters that employ the LMS algorithm for adapting the filter coefficients. The silicon implementation was undertaken on CHIPCRAFTER, utilizing the ES2 1.0 micron CMOS process.