Cascade Of Filter Sections Research Articles

Design Methodology for Nearly Linear-Phase Recursive Digital Filters by Constrained Optimization

A methodology for the design of recursive digital filters having nearly linear phase response is proposed. The underlying design method is of the direct type whereby the filter is designed as a single unit. The design problem is formulated as a cascade of filter sections where each section is represented by a biquadratic transfer function either in the conventional polynomial form or in the polar form. The design problem is then solved using a constrained Newton's method whereby constraints are used to assure the stability of the filter, to control the step size in order to achieve fast convergence, and to eliminate a real-axis pole-migration problem that often interferes with the design process. Several design examples demonstrate that when compared with filters designed using existing state-of-the-art methods, the proposed methodology yields filters having reduced order and/or improved performance.

An analogue VLSI model of periodicity extraction in the human auditory system

This paper presents an electronic system that extracts the periodicity of a sound. It uses three analogue VLSI building blocks: a silicon cochlea, two inner-hair-cell circuits and two spiking neuron chips. The silicon cochlea consists of a cascade of filter sections that filter the input sound. The system uses correlation between two spike trains created from different outputs of the silicon cochlea to obtain very selective filters, i.e., filters that respond only to a very narrow range of periodicities, but that at the same time still respond quickly. This is an advantage over traditional band-pass filters, where an increase in selectivity has to be traded off against a decrease in response time.