Error spectrum shaping in block-state digital filteres
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Roundoff noise in fixed-point digital filters can have an adverse effect on their performance especially when bandwidths are small. Design techniques for reducing the roundoff noise based on the use of ESS were proposed recently. These techniques provide a certain freedom in trading between roundoff noise and hardware complexity. Their usefulness stems from the fact that, a tradeoff between single precision and double precision can be achieved which considerably improves performance, and if the ESS network is chosen carefully, is simpler to implement than the double precision schemes. The idea in this work is to use a particular class of block-state realizations that are derived from optimal and block-optimal simple state-space structures. With this concept, two structures were proposed based on the use of ESS. These structures are called, respectively, error-feedback block-state structure and second order error-feedback block-state cascaded form. We have shown that, if the error-feedback coefficients were chosen properly, a significant reduction in the noise gain can be achieved. The choice of these coefficients has to be based upon the choice of the block length of the block realization. We have also shown that, in narrowband low-pass digital filters,identity matrix as a feedback matrix can perform very weIl over a large set of block lengths (1 to 15). The roundoff noise gain becomes almost independent of the block length. The implementation of such feedback consists of adds only.Furthermore, the numerical examples used in this particular case, showed that the two proposed structures perform almost identically when both using identity matrix as a feedback matrix. So, the second order error-feedback block-state cascaded forro appears to offer an attractive alternative to the error feedback block-state structure since, it uses rouch less multipliers. The implementation of this structure is also simpler and the multiplication rate does not increase quadratically.
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| Cote | Localisation | Type de Support | Type de Prêt | Statut | Date de Restitution Prévue | Réservation |
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| 621.381 LAO TH C1 | BIB-Centrale / Thèses | interne | disponible |