Analog Adaptive Filters

Duration: Half Day

Who Should Attend:
Researchers and designers of digital communication transceivers. This includes people working either at the circuit level (analog, digital, or mixed signal) or the system level. The material would also be of interest to adaptation algorithm researchers.

Adaptation is used whenever a filter's parameters must track poorly controlled or time varying conditions. At low speeds, adaptive filtering is easily and efficiently performed using digital circuits. However, analog filters are preferable when high speed, low power operation is required and moderate linearity can be tolerated. In these cases, the combination of
flexibility and performance offered by analog adaptive filters can be an enabling technology. This tutorial will provide a overview of the area, including the algorithms, architectures, and circuits.

In the first part of the tutorial, analog filter structures suitable for adaptation are presented. Both analog discrete time (transversal, transpose, IIR) and continuous time (Laguerre and ladder filters) filter structures are covered including first order circuit designs.

The second part of the tutorial is a discussion of adaptation strategies suitable for analog filters. The traditional LMS algorithm has several problems when applied to analog adaptive filters. Algorithmic and circuit techniques for combating these problems will be discussed. Alternative adaptation algorithms will also be presented.

Finally, the third part of the tutorial brings together material presented in the first two sections by focusing on practical applications of analog adaptive filters. Both established applications and ongoing research areas will be considered including magnetic storage read channels, Ethernet transceivers, coaxial cable channels, backplanes, chip-to-chip connections, and optical communications. We shall see how the applications dictate the designers' choice of adaptation strategy, filter structure and circuit implementation.

Tutorial Presenter:
- Prof. A. Chan Carusone, University of Toronto, Canada