An Analog Wavelet Chip for Speech Compression

This paper describes the theory and implementation in CMOS technology of a circuit which performs analog wavelet decompositions of a one-dimensional (e.g., sound) input. The circuit is based on the Analog VLSI techniques described by Carver Mead in Analog VLSI and Neural Systems [1]. The analog wavelet outputs are the output of a logarithmically scaled set of bandpass filters; each band is sampled at a rate proportional to the Nyquist rate of the highest frequency content of that band. The result is a matrix of discrete points describing the input signal as a function of both frequency and time. The filter function of each band is gaussian shaped in order to best resolve the uncertainty relation between time and frequency at each sampled point. This chip has been designed by Tim Edwards under the direction of Michael Godfrey, and fabricated by Zilog Corporation of Campbell, California. Zilog provided the funding for this project. 1 Overview This paper describes the Analog Wavelet Tran..