DIGITAL NOTCH FILTERS IMPLEMENTATION WITH FIXED-POINT ARITHMETIC

Eduardo Pinheiro, Octavian Postolache, Pedro Silva Girão

Abstract

Many studies have been developed aiming to improve digital filters realizations, recurring to intricate structures and analysing the error´s behaviour. The work presented in this paper analyses the feasibility of fixed-point implementation of classical IIR notch filters (Butterworth, Chebyshev, Bessel and elliptic), and also the effect of the quality factor and normalized cut-off frequency in the number of significant bits necessary to represent the coefficients, to scrutinize the deformations the filters suffer for distinct design specifications.<br />The work focuses especially in the implementation of power line notch filters used to improve the signal-to-noise ratio in biomedical signals. The obtained results, when quantizing the digital notch filters, show that by applying second order sections decomposition, low-order digital filters may be designed using only part of double precision capabilities, while high-order notch filters with harsh design constrains are implementable using double precision, but only in second-order sections. Thus, it is shown that to optimize computation time in real-time applications, an optimal digital notch filter implementation platform should have variable arithmetic precision.

Keywords

digital filter implementation, digital filter word length effects, notch digital filters

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IMEKO-WC-2009-TC4-504.pdf

DOI

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IMEKO TC

TC4 - Measurement of Electrical Quantities

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