Research Papers - Department of Electrical and Electronic Engineering

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Start date: 1996End date: 1999

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    Robustness of digital filters with respect to limit-cycle behavior under coefficient perturbations
    (International Society for Optics and Photonics, 1996-06-07) Kulasekere, E. C; Premaratne, K; Bauer, P. H
    A digital filter which has been designed to be limit cycle free may exhibit limit cycles at the implementation stage. This is due to the inability to implement filter coefficients exactly in hardware when they are quantized to satisfy available wordlength requirements. Given a digital filter which is limit cycle free under zero input conditions, the work below presents an algorithm which finds a region in the coefficient space, about the nominal filter coefficient values, where in the filter remains limit cycle free. Furthermore the results of the algorithm will also indicate the availability of other machine representable numbers for the coefficients that fall within this robustness region. Hence one may even choose shorter wordlength registers for coefficient storage if the corresponding grid falls within the constructed robustness region.
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    PublicationEmbargo
    An exhaustive search algorithm for checking limit cycle behavior of digital filters
    (IEEE, 1996-10) Premaratne, K; Kulasekere, E. C; Bauer, P. H; Leclerc, L. J
    The presence of limit cycles that may arise in fixed-point arithmetic implementation of a digital filter can significantly impair its performance. This paper presents an algorithm to determine the presence/absence of such limit cycles. For generality, the filter is taken to be in its state-space formulation. The algorithm is applicable independent of filter order, type of quantization nonlinearity, and whether the accumulator is single or double length. It may be utilized to construct limit cycle free regions in filter coefficient space. Once a filter is determined to be limit cycle free, a technique that provides a robustness region in coefficient space where all filters remain limit cycle free is also presented.